Which of the following would most likely be observed in the lung during an autopsy of a 2-week-old
infant who died of neonatal respiratory distress syndrome?
A. Alveoli filled with neutrophils
B. Dense fibrosis of the alveolar walls
C. Enlarged air space
D. Hyaline membranes and collapsed alveoli
E. Normal lung histology for age
Explanation:
The correct answer is D. Neonatal respiratory distress syndrome is a disease of immaturity. The
immature lung is not able to produce sufficient surfactant to prevent collapse of many alveoli.
Severe diffuse damage to alveoli causes precipitation of protein ("hyaline membranes") adjacent
to many alveolar walls. In infants that survive, particularly if oxygen was used for therapy,
the lungs eventually become heavily fibrotic (misnamed bronchopulmonary dysplasia).
Abundant neutrophils (choice A) would not be seen unless the patient had also developed
pneumonia.
Fibrosis (choice B) is a late, not early, feature of respiratory distress syndrome.
The air spaces are collapsed, not enlarged (choice C), in this condition.
The histology in these patients is usually markedly abnormal (not choice E).
A 4 year-old child develops a large erythematous rash around the site of a mosquito bite. One month
later, she is taken to a pediatrician because of a puffy face and swollen ankles. The scanty
urine sample has a reddish-brown hue, and contains both red blood cells and protein. Which of
the following distinctive features would be most likely to be seen on renal biopsy?
A. Fusion of podocyte foot processes
B. IgA in the mesangium
C. Linear IgG deposits
D. Onion-skinning of renal arterioles
E. Subepithelial electron dense humps
Explanation:
The correct answer is E. The disease is poststreptococcal glomerulonephritis, which can follow
either streptococcal pharyngitis (one to two weeks after the infection) or skin infection
(three to six weeks after the infection). The child is showing signs of both nephritis
(hematuria) and nephrosis (puffy face and swollen ankles).The characteristic feature of this
disease on renal biopsy is the presence of subepithelial humps, visible either by light or
electron microscopy.
Fusion of podocyte foot processes (choice A) suggests minimal change disease.
IgA in the mesangium (choice B) suggests Berger's disease.
Linear IgG deposits (choice C) suggests anti-glomerular basement membrane disease, which is
called Goodpasture's disease if it is accompanied by pulmonary damage.
Onion-skinning of renal arterioles (choice D) suggests malignant hypertension.
A 35-year-old man presents to an emergency department with an exquisitely tender prostate gland. An
acute bacterial infection is suspected. Which of the following organisms is the most common
pathogen in this setting?
A. Enterobacter
B. Escherichia
C. Klebsiella
D. Proteus
E. Pseudomonas
Explanation:
The correct answer is B. The disease is acute bacterial prostatitis; the usual route of
infection is by direct extension from a bladder or urethral source. Less commonly, hematogenous
or lymphatic spread from a distant site may occur. The most commonly isolated organism is
Escherichia coli; other common pathogens include Klebsiella,Proteus, Pseudomonas, Enterobacter,
Serratia, Enterococcus, and Staphylococcus aureus.
Enterobacter(choice A), Klebsiella(choice C), Proteus(choice D), and Pseudomonas(choice E) are
all gram-negative rods that can cause acute bacterial prostatitis, but they are not as common
as Escherichia coli.
On rectal examination, a patient is found to have a large, fungating mass protruding into the rectal
lumen. Biopsy of this mass demonstrates an invasive malignant tumor composed of glandular
structures. The development of this condition is most strongly associated with
A. diverticulitis
B. diverticulosis
C. juvenile polyposis syndrome
D. Peutz-Jeghers syndrome
E. ulcerative colitis
Explanation:
The correct answer is E. The disease is adenocarcinoma of the colon. Predisposing conditions
include inflammatory bowel disease (ulcerative colitis more than Crohn's disease) and
adenomatous polyps occurring either as an isolated finding or as part of familial syndromes
including familial polyposis coli, Gardner syndrome, and Turcot syndrome. Western diets high in
fat and protein and low in fiber are also thought to predispose for colon cancer.
Diverticulitis (inflamed diverticula, choice A) and diverticulosis (presence of diverticula in
colon, choice B) do not appear to predispose for colon cancer.
Neither juvenile polyposis syndrome (choice C), in which the polyps consist of mucus-filled
tubules, nor Peutz-Jeghers syndrome (choice D), in which polyps form around an arborizing tree
of connective tissue and smooth muscle, predisposes for colon cancer.
A 3-year-old child is referred to a major medical center because of an abdominal mass arising from his
right adrenal gland. Biopsy of the lesion demonstrates sheets of small cells with
hyperchromatic nuclei containing occasional pseudorosettes composed of circles of tumor cells
with central young nerve fibers arising from the tumor cells. Which of the following oncogenes
is associated with this patient's tumor?
A. erb-B2
B. c-myc
C. L-myc
D. N-myc
E. ret
Explanation:
The correct answer is D. The tumor is a neuroblastoma, which is one of the principal forms of
cancer in children. Neuroblastoma typically occurs before age 5, with many presenting before
age 2. Neuroblastoma can arise from neural crest cells throughout the body, but the adrenal
medulla is the most common site. Homer-Wright pseudorosettes are circles of tumor cells with
central young nerve fibers arising from the tumor cells. The oncogene associated with
neuroblastoma is N-myc.
erb-B2 (choice A) is associated with breast, ovarian, and gastric carcinomas.
c-myc(choice B) is associated with Burkitt's lymphoma.
L-myc(choice C) is associated with small cell carcinoma of the lung.
ret (choice E) is associated with multiple endocrine neoplasia, types II and III.
Which of the following clinical conditions is most likely to result in hoarseness during speech?
A. Bronchogenic carcinoma of the apical segment of the right lung
B. Mitral valve insufficiency
C. Pulmonary thromboembolism
D. Retroesophageal right subclavian artery
E. Thymoma
Explanation:
The correct answer is A. A tumor of the apical segment of the upper lobe may impinge on the
recurrent laryngeal nerve since it ascends from the superior mediastinum to the root of the
neck in a groove between the trachea and esophagus. The recurrent laryngeal nerve supplies all
intrinsic muscles of the larynx except the cricothyroid.
Mitral valve insufficiency (choice B) causes a backup of blood into the left atrium. The
enlarged left atrium exerts pressure on the esophagus, which lies posterior to it, causing
dysphagia (difficulty swallowing).
Pulmonary embolus (choice C) causes an obstruction to arterial blood flow of the lung,
resulting in infarction of the affected segment. It may also cause pleurisy, resulting in pain
conveyed by intercostal nerves.
When the right subclavian artery (choice D) arises from the arch of the aorta, rather than from
the brachiocephalic trunk, it passes posterior to the esophagus to reach the right upper
extremity. This may cause compression of the esophagus, resulting in dysphagia.
Thymoma (choice E), or tumor of the thymus gland, may cause dyspnea (difficulty breathing) due
to pressure on the trachea. It may also cause engorgement of deep and superficial veins of the
neck due to pressure on the superior vena cava.
A 10-year-old girl is brought to the doctor with malaise, pallor, low-grade fever, and weight loss. She
says that she has had several nose bleeds recently. Her complete blood count shows a markedly
elevated white blood cell count. Bone marrow aspirate shows 35% myeloblasts and 55%
erythroblasts. According to the FAB classification, which acute myelogenous leukemia does this
patient have?
A. M2
B. M3
C. M4
D. M5
E. M6
Explanation:
The correct answer is E. The FAB classification (French American British) sorts AML into seven
categories (M1-M7). If the marrow has greater than 30% blasts, of which more than 50% are
erythroblasts, then the diagnosis is M6. The symptoms described are the typical presenting
features of AML. Only half of AML patients actually present with elevated WBCs.
M2 (choice A), or myeloblastic leukemia with maturation, is characterized by greater than 30%
blasts, with more than 50% of the blasts being myeloblasts and promyelocytes. Mature forms are
seen as well. Eosinophils may be heavy in some cases.
M3 (choice B), or hypergranular promyelocytic leukemia, is characterized by greater than 30%
blasts. The majority of cells have a promyelocytic appearance with kidney-shaped nuclei. Auer
rods are usually seen in the cytoplasm.
M4 (choice C), or myelomonocytic leukemia, is characterized by greater than 30% blasts, with
promonocytes and monocytes accounting for more than 20% of the bone marrow aspirate.
M5 (choice D), or monocytic leukemia, is divided into differentiated and poorly differentiated.
There are more than 30% blasts; the granulocyte component is less than 10% of marrow cells. The
monocytes can be detected cytochemically with the fluoride-sensitive esterase reaction.
After an upper respiratory infection, a 33-year-old man develops severe lower back pain. Over the next
several days, severe, generalized muscle weakness occurs, accompanied by distal paresthesia. On
physical examination, weakness is evident, but there is no appreciable sensory loss. Nerve
conduction studies show evidence of demyelination. Over the next 2 months, the patient recovers
with minimal residual sequelae. The mechanism underlying this patient's disease is similar to
the mechanism associated with which of the following diseases?
A. Creutzfeldt-Jakob disease
B. Friedreich ataxia
C. Huntington disease
D. Multiple sclerosis
E. Progressive multifocal leukoencephalopathy
Explanation:
The correct answer is D. The patient has Guillain-Barré syndrome, also known as acute
idiopathic inflammatory polyneuropathy. This condition, which typically follows an upper
respiratory or other infection by several days to a month, is due to an autoimmune attack on
the myelin of peripheral nerves. In this respect, it is most similar to multiple sclerosis,
which is an autoimmune attack on the myelin in the brain and spinal cord. Most cases of
Guillain-Barré syndrome resolve spontaneously. A few patients have recurrences, and rare
patients die during the acute episode of respiratory muscle failure (artificial ventilation may
be required).
Creutzfeldt-Jakob disease (choice A) is an Alzheimer-like condition caused by a prion (protein
infectious agent).
Friedreich ataxia (choice B) is an autosomal recessive disorder associated with spinocerebellar
degeneration. Ataxia and paralysis are seen beginning in adolescence.
Huntington disease (choice C) is an autosomal dominant degeneration of the caudate and frontal
lobes characterized by movement disorder and dementia.
Progressive multifocal leukoencephalopathy (choice E) is due to papovavirus (JC and SV40) brain
infection, which causes demyelination by killing oligodendroglia.
A 54-year-old man presents to a physician with headaches. A complete blood count demonstrates a
hematocrit of 62%. The peripheral smear shows normocellular erythrocytes, with increased
reticulocytes and nucleated red cells. Bone marrow biopsy demonstrates increased numbers of
erythrocytic precursors. Cancer of which of the following organs would be most likely to cause
these findings?
A. Colon
B. Kidney
C. Ovary
D. Prostate
E. Thyroid
Explanation:
The correct answer is B. The hematologic finding is erythrocytosis, which can be caused by
abnormal erythropoietin secretion by renal cell carcinoma (i.e., a paraneoplastic syndrome).
Absolute erythrocytosis also occurs in a number of other conditions, such as hypoxia, other
types of renal disease, some tumors (e.g., hepatocellular carcinoma, meningioma,
pheochromocytoma, cerebellar hemangioblastoma, adrenal adenoma), androgen therapy, Bartter's
syndrome, or in polycythemia vera.
Cancers of the colon (choice A), prostate (choice D), and thyroid (choice E) do not usually
produce inappropriate hormones.
Cancers of the ovary (choice C) can produce male or female sex steroids, but do not produce
erythropoietin.
A 55-year-old diabetic man has a long history of renal failure. He is currently waiting for an organ for
transplant, and has been on hemodialysis in the interim. If this man develops amyloid deposits
around his joints, they are likely to be composed of which of the following substances?
A. Amyloid-associated protein
B. Amyloid light chains
C. Beta2 microglobulin
D. Calcitonin precursors
E. Prealbumin (transthyretin)
Explanation:
The correct answer is C. Amyloid deposits appear similar by light and electron microscopy, but
actually represent a heterogeneous population of proteins that have a common tertiary structure
forming a beta-pleated sheet. Questions about the type of amyloid seen in different disease
states (even though the type is usually not determined clinically) are favorites on examinations.
Here are two tables to help you out:
Systemic amyloidosis: Chronic active disease AA amyloid from serum amyloid- associated
(SAA) protein from liver (choice A) Myelomas and related diseases AL amyloid from immunoglobulin
light chain (choice B) Chronic hemodialysis Beta2 microglobulin (related to high plasma levels)
(choice C) Nephropathic hereditary forms (familial Mediterranean fever) AA amyloid from SAA
(choice A) Cardiomyopathic hereditary forms (senile systemic amyloidosis)
Prealbumin/transthyretin (choice E) Neuropathic hereditary syndromes Prealbumin/transthyretin
(choice E)
Localized amyloidosis: Senile cardiac amyloidosis Atrial natriuretic peptiderelated fibrils Cerebral amyloid in Alzheimer disease, Down syndrome Cerebral amyloid in
Alzheimer disease, Down syndrome Medullary carcinoma of thyroid Calcitonin precursors (choice D)
Isolated, massive, nodular deposits (skin, lung, urogenital tract) AL from light chains (choice
B)
A 22-year-old college student comes to the emergency room complaining of right upper quadrant
abdominal
pain for several hours. He admits to drinking excessive amounts of alcohol 3 days ago. Over the
course of the last few days he recalls that he ingested the contents of an entire bottle of
acetaminophen. On exam he is afebrile, with normal vital signs and slight tenderness in the right
upper quadrant. Which of the following is the most likely set of liver function enzymes in this
patient?
Aspartate aminotransferase (AST) Alanine aminotransferase (ALT) Alkaline
phosphatase Amylase
A. High High High Normal
B. High High Normal Normal
C. High Low High High
D. Normal Normal High Normal
E. Normal High Normal High
Explanation:
The correct answer is B. This patient is suffering from hepatic injury as a result of
acetaminophen overdose. Acetaminophen, when broken down by the liver, produces a hepatotoxic
metabolite that can cause liver necrosis. When ingested in large quantities, massive destruction
may occur, potentially resulting in liver failure and mandatory liver transplant for survival.
This patient's liver is even more susceptible to hepatotoxicity from acetaminophen after an
alcohol binge, which renders it less able to metabolize the toxic byproducts.
Both aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are contained within
liver cells and are released when liver cells are destroyed, as in this case (often these enzymes
can be elevated to tens of thousands in an acute injury). Alkaline phosphatase is primarily
located within the cells of the bile ducts and biliary tree. Thus, an elevation of this enzyme
usually indicates pathology within the biliary tree (i.e., stones within the bile ducts, cancers
in the biliary tree, or other obstructive processes causing damage in the biliary tree). Amylase
is located within several different types of cells, but is used primarily in the diagnosis of
pancreatitis, in which it becomes elevated. Therefore, in this patient, both the AST and ALT would
likely be very high. It is unlikely that there would be any abnormality in the levels of alkaline
phosphatase or amylase.
A child presents with "freckles" all over his body, including the buccal mucosa, lips, palms, soles, and
skin not exposed to sun. Which of the following additional findings would most likely be
present?
A. Colonic polyps
B. Desmoid tumors
C. Epidermoid cysts
D. Osteomas of the jaw
E. Pigmented ocular fundus
Explanation:
The correct answer is A. The widespread "freckles" (spots of melanin pigmentation) described in
this case are associated with hamartomatous colonic polyps in Peutz-Jeghers syndrome. The
polyps in Peutz-Jeghers syndrome do not progress to colon cancer. Interestingly, Peutz-Jeghers
syndrome is associated with an increased potential to develop carcinomas of the pancreas,
breast, ovary, uterus, and lung.
All of the other features listed are components of Gardner's syndrome, a variant of familial
adenomatous polyposis syndrome, which carries a greatly increased risk of colon cancer.
A high school basketball player passes out in the middle of a game. He is rushed to the emergency room,
where he regains consciousness. He claims that just before he fainted, he had difficulty
breathing and experienced palpitations. On physical exam, he has a bifid apical impulse and a
coarse systolic murmur at the left sternal border. The echocardiogram reveals ventricular
hypertrophy with asymmetric septal thickening. Which of the following would you expect on
microscopic examination of his heart muscle?
A. Aschoff bodies
B. Disorganization of myofibrils
C. Infiltration by inflammatory cells
D. Localized fibrous scarring
E. Structures resembling poorly formed vessels
Explanation:
The correct answer is B. Microscopic examination of heart muscle from a patient with
hypertrophic cardiomyopathy reveals short, thick myofibrils arranged in circular patterns
admixed with normal tissue. On electron microscopy, myofibrils and myofilaments appear
disarrayed.
Aschoff bodies (choice A) appear in rheumatic myocarditis and consist of degenerating material
and leukocytes. These occur along with Anitschkow myocytes, which contain "ribbon-like" nuclei
and eosinophilic cytoplasm.
Infiltration by inflammatory cells (choice C) would be expected in association with an
infectious process such as acute bacterial endocarditis.
Localized fibrous scarring (choice D) is associated with myocardial healing after infarction.
Structures resembling poorly formed vessels (choice E) are found in cardiac myxoma, the most
common primary tumor of the heart. The tumor cells are derived from primitive multipotent
mesenchymal cells. They may be sessile or pedunculated masses.
An elderly woman is found dead in her home. Autopsy demonstrates an area of pallor on the apex of her
heart. On microscopic examination, there is coagulative necrosis of the muscles accompanied by
a modest neutrophilic infiltrate, which is focally heavy in some areas. No macrophages or
fibroblasts are seen. Approximately how long before her death did this woman experience a
myocardial infarction?
A. 2 hours
B. 18 hours
C. 3 days
D. 10 days
E. 10 weeks
Explanation:
The correct answer is C. The findings suggest a 2-4 day old myocardial infarction (MI). An MI
becomes visible grossly after about 12 hours (sometimes earlier) as an area of pallor and
eventually, cyanosis. Neutrophils infiltrate the tissue anywhere from 12 to 72 hours after
infarction, with increasing evidence of coagulative necrosis.
At 2 hours (choice A), no changes would likely be evident in the infarcted myocardium.
At about 18 hours (choice B), "waviness" of some myocardial fibers may be apparent
microscopically, and subtle changes in the appearance of the myofibrils producing alternating
densely-colored (contracted) and lightly-colored (expanded) areas can be observed.
At 5 to 10 days (choice D), both macrophages and neutrophils are present and granulation tissue
with fibroblasts is growing in from the edges.
After 7 weeks (choice E), the area of infarction is typically completely replaced by scar
tissue.
A patient with rheumatoid arthritis mentions to her physician that after many years without dental
problems, she has recently had seven dental caries filled. This finding suggests that she
should be evaluated for which of the following diseases?
A. Oral squamous cell carcinoma
B. Polyarteritis nodosa
C. Sjögren's syndrome
D. Systemic lupus erythematosus
E. Thyrotoxicosis
Explanation:
The correct answer is C. Rheumatoid arthritis can coexist with a variety of autoimmune diseases
(including those listed in the answers), but is most frequently associated with Sjögren's
syndrome. Sjögren's syndrome classically presents with keratoconjunctivitis (dry eyes) and
xerostomia (dry mouth, often resulting in dental caries and fissures in the oral mucosa). These
symptoms are due to autoimmune involvement with subsequent scarring of the salivary and
lacrimal glands. Parotid gland enlargement is common, as is vasculitis, Raynaud's phenomenon,
hyperviscosity syndrome, and peripheral neuropathy.
The development of oral squamous cell carcinoma (choice A) is not related to the presence of
dental caries.
Polyarteritis nodosa (choice B) is a systemic necrotizing vasculitis. Patients typically
present with low-grade fever, weakness, and weight loss. Abdominal pain, hematuria, renal
failure, hypertension, and leukocytosis may occur.
Systemic lupus erythematosus (choice D) is an autoimmune disease characterized by vasculitis,
rash, renal disease, hemolytic anemia, and neurologic disturbances.
Thyrotoxicosis (choice E) is not related to the development of dental caries.
Following a week of binge drinking, a patient is admitted with severe upper abdominal pain with
radiation to the back. He describes the pain as steady, but notes that it is more severe when
he lays down on his back. His blood pressure starts to drop, but no source of bleeding is
identified. The patient's white count is within normal limits. Which of the following
laboratory tests will most likely be diagnostic?
A. Antinuclear antibodies
B. IgG levels
C. Reticulocyte count
D. Serum acid phosphatase
E. Serum amylase
Explanation:
The correct answer is E. This is a classic presentation of acute pancreatitis. The other
classic presentation is as a complication of gallstones occluding the pancreatic duct. Many
cases of acute pancreatitis are comparatively mild, but severe cases can cause life-threatening
shock secondary to release of vasoactive substances from the damaged pancreas that is difficult
to treat. Acute pancreatitis is diagnosed by demonstrating elevated serum amylase levels.
Antinuclear antibodies (choice A) are present in a number of autoimmune diseases, such as
systemic lupus erythematosus.
IgG levels (choice B) are not affected by acute pancreatitis.
The reticulocyte count (choice C) is an index of bone marrow function that is used to evaluate
the etiologies of some anemias.
Acid phosphatase (choice D) is produced by the prostate, osteoclasts, muscle, and certain blood
cells, among others.
A 62-year-old man with a 40-pack-year history of cigarette smoking, who had a malignant melanoma on
his
neck 5 years ago, presents to the emergency room with acute intestinal obstruction. Laparoscopic
examination of his abdomen demonstrates multiple, large, white masses on the serosa of his small
bowel. This patient most likely has which of the following?
A. An inflammatory lesion
B. Metastatic lung cancer
C. Metastatic melanoma
D. Primary intestinal lymphoma
E. Pseudomyxoma peritonei
Explanation:
The correct answer is C. The obvious answer is correct. The serosal surface of the intestines
is a common metastatic site for melanoma, and is an unusual site for other tumors not located
in the abdomen or pelvis (tumors of the abdominal and pelvic organs can seed the peritoneal
fluid by direct extension, producing tumor throughout the abdominal cavity). An important
feature of melanoma is that the metastatic lesions are often not obviously pigmented, and may
even be amelanotic when observed microscopically. The production of visible melanin pigment
requires that the tumor cells retain a sophisticated level of differentiation, and many of the
more aggressive (which are more likely to metastasize) components of the tumor may have lost
this function. The immunohistochemical tumor markers S-100 and HMB-45 can be very helpful in
these cases in establishing that the masses are indeed melanoma.
An inflammatory etiology (choice A) is unlikely, given the presence of the serosal masses.
Metastatic lung cancer (choice B) would be unlikely to metastasize to the bowel serosa.
Primary intestinal lymphomas (choice D) are quite rare compared with metastatic melanoma in a
patient with previous melanoma.
Pseudomyxoma peritonei (choice E) is associated with seeding of the abdomen with gelatinous
implants rather than discrete masses, often from a mucinous cystadenoma or cystadenocarcinoma
of the ovary or appendix.
A 68-year-old, well-developed, well-nourished black male presents to the emergency department
complaining of shortness of breath. He denies chest pain. He has no significant past medical
history and takes no medications. A chest x-ray shows clear lung fields, mild cardiomegaly and
a widened thoracic aorta with linear calcifications. An MRI of the chest shows aortic
dilatation in the thorax, extending proximally, with atrophy of the muscularis and wrinkling of
the intimal surface. What is the most likely etiology of this condition?
A. Atherosclerosis
B. Hypertension
C. Marfan's syndrome
D. Syphilis infection
E. Takayasu's arteritis
Explanation:
The correct answer is D. Although rare now because of advances in treatment, syphilitic
aortitis and aneurysm are still seen, especially in underserved populations. This complication
generally occurs 10 to 40 years after initial infection. The vasa vasorum of the aorta
undergoes obliterative endarteritis, leading to atrophy of the muscularis and elastic tissues
of the aorta and dilatation. Linear calcifications are often seen in the ascending aorta by xray. The intimal wrinkling or "tree barking" is also a common feature. Syphilitic aneurysm can
be associated with respiratory distress, cough, congestive heart failure and rarely, rupture.
Atherosclerosis (choice A) is the most common cause of aortic aneurysms. These are most often
located in the abdominal aorta, distal to the renal arteries. Intimal wrinkling and linear
calcifications are not seen.
Hypertension (choice B) is usually responsible for dissecting aneurysms located within 10 cm of
the aortic valve. Patients present with sudden chest pain, which is usually severe and tearing
in nature. The chronic hypertension causes a cystic medial necrosis, allowing the separation of
vessel layers.
Marfan's syndrome, an autosomal dominant connective tissue disorder (choice C) is also
associated with dissecting aneurysms, usually of the ascending aorta. The patients are often
very tall with arachnodactyly and ligamentous laxity. Their life-span is generally shortened.
This patient's description and age are not consistent with this diagnosis.
Takayasu's arteritis (choice E) is a syndrome characterized by ocular disturbances and weak
pulses in the arms. It occurs most frequently in young females. It is considered a giant cell
arteritis, and does not cause aneurysms.
An 18-year-old is brought to the emergency room following an automobile accident. Serum enzyme studies
demonstrate a thousand-fold elevation of creatine kinase (CK). Which of the following tissues
is most likely to be the source of the enzyme?
A. Bone
B. Brain
C. Heart
D. Kidney
E. Skeletal muscle
Explanation:
The correct answer is E. Creatine kinase occurs in several different forms, or isoenzymes, in
the body. Most tissues contain a mix of creatine kinase isoenzymes, but one species often
predominates. The MB isoenzyme of creatine kinase is associated with heart damage; the MM
isoenzyme is associated with muscle damage; and the BB isoenzyme is associated with brain
damage. Surgery and trauma are commonly implicated as causes of sufficient skeletal muscle
trauma to markedly elevate creatine kinase. If isoenzyme studies are done, the CK-MM (skeletal
muscle isoenzyme) isoenzyme will be elevated much more markedly than the CK-MB isoenzyme.
Bone (choice A) is not a significant source of CK.
Brain (choice B) can occasionally be a source of creatine kinase (BB isoenzyme), but would not
usually be the major source following an automobile accident.
Heart damage (choice C), as in myocardial infarction (unlikely at this age), can elevate
creatine kinase, but would not usually be the major source in an automobile accident. If the
dilemma arises as to whether an automobile accident was possibly secondary to a myocardial
infarction, the ratio of CK-MB to total CK may be helpful in demonstrating a cardiac
contribution (CK-MB is characteristic of heart muscle).
Kidney (choice D) is not a major source of creatine kinase.
In the course of a laryngoscopic examination for hoarseness, a small lesion is found on the true vocal
cord of a 57-year-old male smoker. On biopsy, severe squamous dysplasia is noted. If untreated,
this lesion may progress to which of the following?
A. Adenocarcinoma
B. Lymphoepithelioma
C. Mucoepidermoid carcinoma
D. Squamous cell carcinoma
E. Squamous papilloma
Explanation:
The correct answer is D. Squamous cell carcinoma is the most frequent type of cancer of the
larynx. As with squamous cell carcinoma of the uterine cervix, the development of laryngeal
carcinoma is related to an orderly sequence of morphologic changes. These begin with epithelial
hyperplasia, proceed through increasingly severe degrees of dysplasia up to in situ carcinoma,
and culminate with invasive carcinoma. Cigarette smoking is the most important risk factor for
the development of laryngeal carcinoma.
Adenocarcinoma (choice A) and mucoepidermoid carcinoma (choice C) are rare forms of laryngeal
cancer. Squamous dysplasia is not a precursor of either type of tumor.
Lymphoepithelioma (choice B) is a form of squamous cell carcinoma that most frequently occurs
in the nasopharynx, although it has been reported in the larynx as well. Its name is derived
from the fact that the tumor is rich in lymphocytes. This tumor occurs frequently in southern
China and certain regions in Africa. Epstein-Barr virus is implicated in its pathogenesis.
Squamous papilloma (choice E) is a benign laryngeal neoplasm caused by human papillomavirus
types 6 and 11. It is not associated with squamous dysplasia.
A patient presents to the emergency room with malaise. The physician notices slight jaundice. Serum
chemistries reveal marked elevation of both aspartate aminotransferase (AST) and alanine
aminotransferase (ALT), with the AST/ALT ratio being 2.5. Alkaline phosphatase is near normal.
Serum copper and serum iron are normal. Liver damage from which of the following diseases most
likely accounts for these findings?
A. Alcoholic hepatitis
B. Biliary cirrhosis
C. Hemochromatosis
D. Hepatitis A
E. Wilson's disease
Explanation:
The correct answer is A. Elevated AST and ALT with a AST/ALT ratio of greater than 1.5 is
strongly suggestive of alcoholic hepatitis. Microscopic features of this condition include
swollen and necrotic hepatocytes, neutrophil infiltration, Mallory (hyaline) bodies, fatty
change, and fibrosis around the central vein.
Biliary cirrhosis (choice B) would be associated with elevated alkaline phosphatase.
Hemochromatosis (choice C) would be associated with elevated serum iron levels.
In viral hepatitis (choice D), both AST and ALT are elevated, but the ratio is usually less
than 1.5.
In Wilson's disease (choice E), serum copper levels are usually raised, and ceruloplasmin (the
copper-carrying protein) levels are lowered.
A 47-year-old executive consults his physician with complaints of feeling tired and several months of
abdominal pain and "dark-colored" urine. The physician does a physical examination and notes
that the patient is slightly jaundiced, and his gallbladder is palpable, but not tender. Which
of the following disorders is most likely, given this presentation?
A. Acute cholecystitis
B. Amyloidosis
C. Hepatic cirrhosis
D. Hepatoma
E. Pancreatic cancer
Explanation:
The correct answer is E. Carcinoma of the pancreas is often associated with vague, non-specific
symptoms such as abdominal pain, but it may be initially asymptomatic. Jaundice is found in the
majority of patients with cancers of the head of the pancreas, along with an enlarged, palpable
gallbladder (Courvoisier's sign) without significant tenderness or other signs of
cholecystitis.
A 35-year-old roofer presents to his primary care physician complaining of dyspnea and chronic dry
cough. Chest x-ray reveals pulmonary hyperinflation with "honeycombing" and calcified parietal
pleural plaques. The most likely diagnosis is
A. anthracosis
B. asbestosis
C. berylliosis
D. byssinosis
E. silicosis
Explanation:
The correct answer is B. This question concerns a USMLE-favorite topic—pneumoconioses. Be
sure to know the classic clues associated with each of the answer choices to this question.
Asbestosis is a disease caused by a family of fibrous silicates commonly found in shipyards,
insulation, and roofing industries. Many years after exposure, patients complain of dyspnea and
chronic dry cough, along with recurrent respiratory infections (especially viral) and weight
loss. Classic pathological findings include lower lobe interstitial fibrosis with septal wall
widening, worse near the periphery of the lung. Chest x-ray often reveals hyperinflation of the
normal parenchyma leading to "honeycombing." Calcified parietal pleural plaques are also
commonly present. Secondary bronchiectasis may complicate the picture.
Anthracosis (choice A) is due to the inhalation of carbonaceous particles by city dwellers,
cigarette smokers, and miners. Deposition of carbon dust can be seen as black pigment in lung
parenchyma, pleura, and lymph nodes. When isolated, it is not associated with systemic disease.
Berylliosis (choice C) is due to heavy exposure to airborne beryllium or its salts. Because of
its high tensile strength and resistance to heat and fatigue, beryllium is used in the
electronic, ceramic, aerospace, and nuclear energy industries. Disease due to beryllium probably
represents a type IV hypersensitivity reaction, with noncaseating granuloma formation and
eventual fibrosis. There is increased risk of bronchogenic carcinoma.
Byssinosis (choice D) is a type of hypersensitivity pneumonitis that can occur with exposure to
cotton, linen, or hemp exposure. It is associated with histamine-related bronchospasm.
Silicosis (choice E) occurs with prolonged exposure to silica dust (mining, glass production,
sand blasting, farming, and road construction). This insidious disease can progress to
respiratory failure and death, and is associated with increased risk for tuberculosis. Classic
x-ray findings include calcified lymph nodes that produce an "eggshell" pattern. The disease
initially involves the upper lobes and perihilar region. Pleural involvement creates dense
fibrous plaques and adhesions that may obliterate the pleural cavities. Uninvolved parenchyma
tends to be hyperinflated and emphysematous.
An 80-year-old woman dies after a long history of progressive memory loss, apraxia, and recurrent
episodes of confusion. In the last months of life she was bedridden and unable to recognize
familiar faces and objects. The pathologist identifies numerous flame-shaped intracytoplasmic
inclusions in neurons of the neocortex and hippocampus. These consist of paired helical
filaments (PHFs) on electron microscopy. Which of the following biochemical changes most likely
accounts for the development of PHFs in this condition?
A. Abnormal degradation of amyloid precursor protein (APP)
B. Abnormal phosphorylation of tau
C. Accumulation of advanced glycosylation end (AGE) products
D. Increased expression of APP
E. Precipitation of insoluble α-tubulin
Explanation:
The correct answer is B. This patient has all of the characteristic clinical features of
dementia (memory loss, apraxia, and confusion). The intraneuronal inclusions found at autopsy
are neurofibrillary tangles. These appear as intracytoplasmic aggregates with a typical flame
shape and are composed of bundles of PHFs twisted around each other. PHFs result from abnormal
phosphorylation of a microtubule-associated protein called tau. Normally, tau is a soluble
protein that regulates tubulin polymerization. Excessive or abnormal phosphorylation converts
tau into an insoluble protein that precipitates as PHFs, filling the cytoplasm of neurons and
disrupting axoplasmic transport.
APP is a normal transmembrane protein of obscure function; the gene for APP is on chromosome
21. Aβ amyloid is a 40 amino acid residue protein that originates from APP and forms the
core of senile plaques. Abnormal degradation of APP (choice A) is thought to be the crucial
event leading to formation of Aβ amyloid in sporadic and familial Alzheimer disease, while
increased expression of APP (choice D) leads to accumulation of Aβ amyloid in the brains
of patients with trisomy 21. Neither mechanism is the direct cause of PHF formation.
Advanced glycosylation end (AGE) products (choice C) are insoluble proteins (mostly collagen
and other long-lived proteins) that accumulate progressively in vessel walls as a result of
glycosylation. This is a mechanism underlying damage in diabetes mellitus and aging, but not in
PHF formation.
The function of tubulin, which is the main component of microtubules, is probably altered in
Alzheimer disease as a result of abnormal phosphorylation of tau and formation of PHFs.
However, precipitation of insoluble α-tubulin (choice E) has not been shown to occur in
Alzheimer disease.
A neonate has a large, purplish, slightly raised lesion on the skin of the forehead near the temporal
area. As the child grows, the lesion grows as well and becomes increasingly prominent. This
lesion may be a component of which of the following syndromes or diseases?
A. Buerger's disease
B. Milroy's disease
C. Osler-Weber-Rendu disease
D. Sturge-Weber syndrome
E. Von Hippel-Lindau disease
Explanation:
The correct answer is D. The lesion is a port-wine stain, which is a purple, flat
telangiectasia (vascular ectasia) that tends to occur on the head and to grow with the body.
These lesions, particularly when they lie in the distribution of the trigeminal nerve, may be
associated with angiomatous masses of the nearby leptomeninges as part of the Sturge-Weber
syndrome. Other features of Sturge-Weber syndrome include mental retardation, seizures, and
hemiplegia.
Buerger's disease (choice A) is a vasculitis especially affecting young men who are heavy
smokers.
Milroy's disease (choice B) is a congenital lymphatic malformation.
Osler-Weber-Rendu disease (choice C) is associated with multiple telangiectasias, but they are
usually small, rather than large.
Von Hippel-Lindau disease (choice E) is associated with cavernous hemangiomas, rather than a
port-wine stain.
A 3-year-old child is evaluated by a pediatrician for poor growth despite excessive food intake. The
mother reports that the child's stools are bulky, foul-smelling, and difficult to flush because
they float. Determination of which of the following would most likely be diagnostic in this
case?
A. Na+ in cerebrospinal fluid
B. Na+ in serum
C. Na+ in sweat
D. Na+ in urine
E. Na+ in whole blood
Explanation:
The correct answer is C. This is one of three common presentations for cystic fibrosis, which
is a common genetic recessive disorder in the Caucasian population. The two other common
presentations are meconium ileus in infancy and multiple respiratory tract infections, often in
later childhood. Cystic fibrosis was the first genetic disease for which a specific lab test
was developed: the sweat test. This test is still used diagnostically; in its modern form, in
which pilocarpine is used to stimulate sweat secretion. The basic underlying defect in cystic
fibrosis is an abnormality of the chloride channel, but both the Na+ and Cl- content of the
sweat of affected children is increased compared to normal.
The Na+ content of CSF (choice A), serum (choice B), urine (choice D), and whole blood (choice
E) is normal in children with cystic fibrosis.
A 45-year-old woman presents to her physician because of a severe "sore throat." Physical examination
demonstrates fever and an extremely tender, enlarged thyroid gland, but no throat erythema.
Serum thyroid studies demonstrate a mild degree of hyperthyroidism. Two months later, the
patient is asymptomatic, and thyroid function tests have returned to normal. She never again
experiences difficulty with her thyroid function. Which of the following was the most likely
cause of her hyperthyroidism?
A. Diffuse nontoxic goiter
B. Graves disease
C. Hashimoto's thyroiditis
D. Subacute granulomatous thyroiditis
E. Subacute lymphocytic thyroiditis
Explanation:
The correct answer is D. This patient most likely has subacute granulomatous (de Quervain's)
thyroiditis, which frequently develops after a viral infection. Microscopically, it is
characterized by microabscess formation within the thyroid, eventually progressing to
granulomatous inflammation with multinucleated giant cells. Clinically, patients may experience
fever, sudden painful enlargement of the thyroid, and/or symptoms of transient hyperthyroidism.
The disease usually abates within 6 to 8 weeks.
Diffuse nontoxic goiter (choice A) by definition does not produce hyperthyroidism.
The hyperthyroidism of Graves disease (choice B) does not spontaneously remit.
Hashimoto's thyroiditis (choice C) can cause transient hyperthyroidism, but then goes on to
cause hypothyroidism.
Subacute lymphocytic thyroiditis (choice E) can cause transient hyperthyroidism, but is
characteristically painless.
A macroscopic hepatic change known as nutmeg liver is indicative of
A. acute left-sided heart failure
B. acute right-sided heart failure
C. alcohol toxicity
D. chronic congestive heart failure
E. liver cirrhosis
Explanation:
The correct answer is D. Chronic heart failure results in blood stasis in the central veins and
central sinusoids of hepatic lobules, with subsequent central hemorrhagic necrosis. Thus, the
red central regions compared with the surrounding tan-brown viable parenchyma impart the
mottled appearance of a nutmeg to the liver cut surface.
Acute left-sided heart failure (choice A) gives rise to acute pulmonary edema, with
extravasation of plasma and red blood cells into alveolar spaces.
Acute right-sided heart failure (choice B) leads to acute congestion of the liver, which does
not acquire the typical nutmeg appearance as in chronic congestion.
Alcohol toxicity (choice C) leads to a number of hepatic alterations. Fatty change results from
alteration in lipoprotein metabolism, leading to accumulation of fats as a large single droplet
within the cytoplasm of hepatocytes (microvesicular steatosis). Alcoholic hepatitis is an acute
response to alcohol abuse and is associated with hepatocyte necrosis and formation of Mallory
bodies. Long-standing alcohol toxicity may cause a perturbation of the liver architecture
leading to liver cirrhosis.
Liver cirrhosis (choice E) is an end-stage condition that may be caused by a number of chronic
insults, such as alcohol toxicity, viral hepatitis B or C, and hemochromatosis. It results from
simultaneous degeneration and regeneration of the liver parenchyma with formation of broad
scars connecting portal spaces. The normal liver architecture is entirely lost and replaced by
regenerating nodules. The nodular pattern is the distinguishing macroscopic feature that allows
easy diagnosis, even on gross examination.
A 32-year-old male with a history of chronic drug abuse presents to his primary care physician
complaining of uncontrollable shaking in his hands. He moves very slowly and walks with a stooped
posture and shuffling gait. Physical exam reveals cogwheel rigidity, a pill-rolling tremor, and
masked facies. His condition deteriorates, and he eventually dies. Structures similar to which of
the following would be expected on autopsy?
A. Hirano bodies
B. Lewy bodies
C. Lipofuscin granules
D. Negri bodies
E. Neurofibrillary tangles
Explanation:
The correct answer is B. This patient has irreversible parkinsonism induced by a contaminant of
illicit drugs–methylphenyltetrahydropyridine (MPTP), a meperidine analog. The parkinsonism
is caused by the drug's destruction of dopaminergic neurons in the substantia nigra. The clinical
signs and symptoms described in the question are classically associated with parkinsonism. Lewy
bodies are neuronal inclusions that are characteristic of Parkinson's disease. The latest
research suggests that structures resembling immature Lewy bodies appear in MPTP-induced
parkinsonism.
Here's an important point on strategy: always take note of the patient's age and descriptors,
such as "chronic drug user." They often provide important clues to the correct answer.
Hirano bodies (choice A) are intraneuronal, eosinophilic rod-like inclusions in the hippocampus
that are associated with Alzheimer's disease. They may occur in normal elderly brains as well.
Lipofuscin granules (choice C) are pigmented cytoplasmic inclusions that commonly accumulate with
aging. They are believed to be residual bodies derived from lysosomes.
Negri bodies (choice D) are intracytoplasmic inclusions that are pathognomonic for rabies. They
are found in the pyramidal cells of the hippocampus, the brainstem, and the Purkinje cells of the
cerebellum.
Neurofibrillary tangles (choice E) consist of intracytoplasmic degenerated neurofilaments and are
seen in patients with Alzheimer's disease. Amyloid plaques are also commonly seen in Alzheimer's.
A 32-year-old woman with systemic lupus erythematosus (SLE) and chronic renal failure manifests rapidly
progressive weakness. On physical examination, she appears pale and has slightly yellow sclerae
and an enlarged spleen. Blood tests reveal severe anemia and mild, mostly unconjugated,
hyperbilirubinemia. Coombs test is positive at 37 C but negative at 0-4 C. This patient
developed anemia because of
A. bone marrow aplasia
B. IgG directed against red blood cells
C. IgM directed against red blood cells
D. renal failure
E. spleen sequestration
Explanation:
The correct answer is B. First, what type of anemia is it? It must be a hemolytic form, since
it is associated with unconjugated hyperbilirubinemia (hence the yellow sclerae), resulting
from increased destruction of red blood cells. Increased erythrocyte destruction is the cause
(not the effect) of splenomegaly. Furthermore, a positive Coombs test implies that hemolysis is
mediated by antibodies attached to red blood cells. Thus, the correct choice must be either IgG
or IgM. Since the Coombs test is positive at warm temperature (37 C), the antibody is a warm
agglutinin. Warm agglutinins are virtually always of IgG type and may be triggered by a variety
of disorders, including lymphomas, drugs, and autoimmune diseases such as SLE. IgG-coated red
cells are then sequestered by the spleen, where hemolysis occurs, thus explaining splenomegaly.
By contrast, cold agglutinins are IgM (choice C) and can be demonstrated by Coombs test at cold
temperature (0-4 C). Cold agglutinins are usually triggered by Mycoplasma pneumoniae infection
or lymphomas.
Bone marrow aplasia (choice A) is due to failure or suppression of myeloid stem cells, with
decreased production of red blood cells, platelets, and leukocytes (pancytopenia). Most
commonly, this condition is caused by chemical agents (especially drugs such as
chloramphenicol, phenylbutazone, alkylating agents, and antimetabolites) or total body
irradiation.
Renal failure (choice D) causes normochromic, normocytic anemia because of decreased synthesis
of erythropoietin. Erythropoietin administration is currently the standard treatment for this
form of anemia. Although renal failure is a frequent consequence of SLE, there is no evidence
that it plays a role in this patient's anemia.
Spleen sequestration (choice E) may cause anemia in case of massive splenomegaly because of an
exaggeration of the normal role of the spleen as repository of blood cells.
A primiparous woman at term experiences placental abruption and is rushed to the operating room for
emergency Cesarean section. Although the newborn recovers well from the delivery, the mother
develops shortness of breath, cyanosis, and copious bleeding from her surgical wounds. Levels
of which of the following blood components is expected to rise in this setting?
A. Factor V
B. Fibrin degradation products
C. Fibrinogen
D. Plasminogen
E. Platelets
Explanation:
The correct answer is B. DIC or consumptive coagulopathy represents pathological activation of
the coagulation system by another underlying disease, with consequent consumption and depletion
of the cellular and humoral components of the coagulation cascade. The fibrinolytic mechanisms
are also activated, and an uncontrolled cycle of bleeding and clotting develops. As a
consequence, levels of all clotting proteins (choices A and C) become depleted, platelet counts
drop (choice E), and the fibrinolytic proteins are depleted as well (choice D). Fibrin
degradation products (choice B), which are normally low in the serum, rise markedly in this
disease; identification of these proteins can be an important indicator of DIC.
A 38-year-old male has paroxysmal hypertension. He is subsequently found to have medullary carcinoma
of
the thyroid, pheochromocytoma, and mucosal neuromas. Parathyroid involvement is not noted. What
is the most likely diagnosis?
A. MEN type I
B. MEN type II
C. MEN type III
D. Sipple's syndrome
E. Wermer's syndrome
Explanation:
The correct answer is C. MEN III, also known as MEN IIb, is characterized by medullary thyroid
carcinoma, pheochromocytoma, and mucosal neuromas.
Wermer's syndrome is also called MEN type I (choices A and E). It is characterized by
pancreatic (insulinoma), pituitary, and parathyroid involvement.
Sipple's syndrome, or MEN type II (choices B and D), is similar to MEN III, but it has
parathyroid involvement (tumor or adenoma) as opposed to neuromas.
Bilateral ovarian masses are identified on pelvic examination of a 40-year-old woman. Ultrasound
examination reveals multiloculated cystic masses involving both ovaries. The patient is treated
with total abdominal hysterectomy with removal of both adnexa. Pathologic examination
demonstrates papillary carcinoma producing serous fluid. Which of the following tumor markers
would be most useful in monitoring for recurrence?
A. Alpha-fetoprotein
B. Bombesin
C. CA-125
D. PSA
E. S-100
Explanation:
The correct answer is C. The tumors are serous papillary cystadenocarcinomas of the ovaries.
These tumors express CA-125 and are apparently derived from the surface epithelium of the
ovaries.
Alpha-fetoprotein (choice A) is not produced by this type of ovarian tumor, but can be produced
by testicular tumors, and less commonly, by ovarian tumors with a yolk sac tumor component.
Bombesin (choice B) is a marker for neuroblastoma, small cell carcinoma, gastric carcinoma, and
pancreatic carcinoma.
PSA (choice D) is a marker for prostatic carcinoma.
S-100 (choice E) is a marker for melanoma, neural tumors, and astrocytomas.
A middle-aged woman presents to her physician with fatigue, pruritus, and steatorrhea. Further studies
demonstrate sclerosing cholangitis and the presence of antimitochondrial antibodies. This
patient, if left untreated, is also at increased risk of developing which of the following?
A. Markedly decreased PaO2
B. Markedly decreased serum uric acid
C. Markedly increased serum cholesterol
D. Markedly increased serum pyruvic acid
E. Markedly increased serum pH
Explanation:
The correct answer is C. The patient's disease is primary biliary cirrhosis, which is an
autoimmune disease characterized by sclerosing cholangitis and cholangiolitis. The most helpful
clue in the question stem is the antimitochondrial antibody, which is present in over 90% of
the patients. The course is usually slowly progressive over 5-25 years. Patients are sometimes
diagnosed when routine blood tests demonstrate an elevated alkaline phosphatase. In addition to
the features listed in the question, patients with advanced disease tend to develop profound
hypercholesterolemia and xanthomas.
In a hospital cardiac care unit, there are three patients with different cardiac conditions: a 52-yearold man with dilated cardiomyopathy, an 18-year-old girl with mitral valve prolapse, and a 30year-old man with infective endocarditis of the mitral valve. Which of the following features do
all these patients most likely share?
A. Decreased compliance
B. Depressed myocardial contractility
C. Infectious etiology
D. Mitral valve stenosis
E. Risk of systemic thromboembolism
Explanation:
The correct answer is E. Systemic thromboembolism may develop in each of these patients.
Vegetations associated with infective endocarditis may undergo fragmentation and result in
systemic thromboembolism. Stasis develops in dilated ventricles, which predisposes to formation
of thrombi attached to the ventricular walls (mural thrombi). Mural thrombi may also form
within the left atrium in the presence of mitral valve prolapse. Thromboemboli may originate
from mural thrombi.
Decreased compliance (choice A) is a pathophysiologic alteration present in a variety of
cardiac disorders in which there is impediment to expansion or relaxation of ventricular walls,
such as restrictive cardiomyopathy, hypertrophic cardiomyopathy, and constrictive pericarditis.
This feature is not present in any of the conditions described in the question.
Depressed myocardial contractility (choice B) results from conditions that impair myocardial
inotropism, such as dilated cardiomyopathy and ischemic heart disease. Depressed inotropism is
not present in infective endocarditis or mitral valve prolapse.
Of the three conditions in the question stem, only infective endocarditis is definitely related
to an infectious etiology (choice C), usually bacteria. Recall that mitral valve prolapse is
due to myxomatous degeneration of the mitral valve, sometimes associated with Marfan syndrome.
The etiology of dilated cardiomyopathy is heterogeneous, and most cases are idiopathic. Of the
remaining cases, viral infections, toxic insults (especially alcohol), metabolic disorders
(hemochromatosis), pregnancy, and genetic influences are the underlying causes.
Mitral valve stenosis (choice D) may develop as a result of vegetations forming on the mitral
valve and occluding the valvular orifice. Endocarditis of the mitral valve more often leads to
mitral insufficiency because of destruction of valve leaflets or rupture of chordae tendineae.
On the contrary, both mitral valve prolapse (usually clinically silent) and dilated
cardiomyopathy may lead to mitral valve insufficiency and regurgitation.
A teenager brought to the emergency room is noted to be hyperventilating. Blood gas studies demonstrate
both a respiratory alkalosis and a metabolic acidosis. This presentation is most suggestive of
poisoning with which of the following agents?
A. Acetaminophen
B. Carbon monoxide
C. Lead
D. Mercury
E. Salicylates
Explanation:
The correct answer is E. It is worth learning the presentations of the common poisons listed in
the answer choices, because a timely diagnosis can sometimes save a patient's life. The
presentation of the teenager in the question is typical for salicylate poisoning, including
poisoning with aspirin. Fatalities are typically due to dehydration and hypokalemia.
In contrast to the acute toxicity of salicylates, acetaminophen (choice A) poisoning produces
nausea, vomiting, abdominal pain, and shock in some cases; it can cause irreversible hepatic
failure (which can be prevented or ameliorated by administration of N-acetylcysteine) 2-6 days
after ingestion.
Carbon monoxide (choice B) causes hypoxia, and a cherry red coloration of the lips and mucos
membranes may be evident.
Lead and mercury poisoning are both usually seen in their chronic forms, although mercury
ingestion can produce an acute toxicity with renal tubular necrosis and necrosis of
gastrointestinal epithelium. Chronic lead poisoning (choice C) can cause anemia (with
basophilic stippling of RBCs), neuropathy, and abdominal pain. Chronic mercury poisoning
(choice D) causes CNS atrophy, gingivitis, gastritis, and renal tubular changes.
A 60-year-old man with a 5-year history of stable angina pectoris sustains a head injury in an
automobile accident and dies. The family is contacted and consents to an autopsy. Microscopic
examination of a section of heart muscle would most likely reveal which of the following
pathologic findings?
A. Coagulative necrosis of the subendocardial muscle
B. Dense scar localized to the distribution of one coronary artery
C. Focal fibrosis and subendocardial myocardial vacuolization
D. Heavy neutrophilic infiltrate adjacent to a large area of coagulative necrosis
E. Transmural coagulative necrosis
Explanation:
The correct answer is C. Repeated episodes of stable angina pectoris typically cause gradual
loss of myocytes, which is seen pathologically as small patches of fibrosis and vacuolization
of damaged myocytes, typically in subendocardial locations (which are relatively poorly
perfused). The other answers describe features that may be seen in true myocardial infarctions,
of either the subendocardial or transmural type.
An elderly woman complains to her physician that her eyes and mouth are always dry. She also has
complaints of arthritis. What form of arthritis would most likely be diagnosed in this patient?
A. Gonococcal arthritis
B. Gouty arthritis
C. Osteoarthritis
D. Pseudogout
E. Rheumatoid arthritis
Explanation:
The correct answer is E. Dry eyes and mouth in an elderly woman are probably due to Sjögren's
syndrome, which is an autoimmune attack on the salivary and tear glands. Sjögren's syndrome is
associated, in some cases, with rheumatoid arthritis.
Gonococcal arthritis (choice A) is a systemic complication of gonorrhea, typically observed in
young women who have had a recent sexual encounter.
Gout (choice B) and pseudogout (choice D) can cause arthritis secondary to crystal deposition
in joints.
Osteoarthritis (choice C) appears to be due to repetitive low-level trauma to joints.
Biopsy of an ulcerated gastric lesion of a 60-year-old smoker demonstrates glands containing cells with
enlarged, hyperchromatic nuclei below the muscularis mucosa. Two tripolar mitotic figures are
noted. With which of the following infectious agents has this type of lesion been most strongly
associated?
A. Epstein-Barr virus
B. Helicobacter pylori
C. Human papilloma virus
D. Molluscum contagiosum virus
E. Schistosoma haematobium
Explanation:
The correct answer is B. The patient has gastric carcinoma, which has been strongly linked, in
at least some studies, to prior gastric infection with Helicobacter pylori. H. pylori has also
been implicated in the etiologies of gastric peptic ulcer, chronic gastritis, and
(questionably) gastric lymphoma.
Epstein-Barr virus (choice A) has been linked to African Burkitt's lymphoma and nasopharyngeal
carcinoma.
Human papilloma virus (choice C) has been linked to a variety of warts, condyloma, and genital
cancers.
Molluscum contagiosum virus (choice D) is a poxvirus that causes small tumor-like papules of
the skin.
Schistosoma haematobium(choice E) has been linked to bladder cancer.
A 20-year-old black woman with a history of multiple small bowel resections for Crohn's disease presents
complaining of fatigue and dyspnea on exertion. Her physical examination is notable for pallor
and a wide-based, unsteady gait. Her lab studies reveal a hemoglobin of 10.0 g/dl with a mean
corpuscular volume of 120 µm3. Examination of the peripheral blood smear shows macrocytosis,
anisocytosis, poikilocytosis, and neutrophils with 6-8 nuclear lobulations. The most likely
cause of this patient's anemia is
A. beta-thalassemia trait
B. folate deficiency
C. iron deficiency
D. sickle cell trait
E. vitamin B12 deficiency
Explanation:
The correct answer is E. The patient has a macrocytic anemia with hypersegmented neutrophils.
This picture is consistent with either folate or vitamin B12 deficiency. The history of small
bowel resections and the presence of neurological signs on physical examination tip the
diagnosis to B12 deficiency.
Beta-thalassemia trait (choice A) causes a microcytic, not a macrocytic, anemia.
Folate deficiency (choice B) causes a similar picture on peripheral blood smear but is not
associated with neurological signs and symptoms.
Iron deficiency (choice C) causes a microcytic, not a macrocytic, anemia.
Sickle cell trait (choice D) does not cause anemia and is associated with a normal peripheral
blood smear under usual physiologic conditions.
A 35-year-old man returns to the U.S. after a recent trip to Central America. A few days later, he
develops altered consciousness and extreme irritability. All diagnostic investigations and
supportive therapy are unsuccessful, and the patient becomes comatose and dies. Autopsy reveals
elongated eosinophilic intracytoplasmic inclusions within the pyramidal neurons of the
hippocampus and Purkinje neurons of cerebellum. Which of the following is the most likely
diagnosis?
A. CMV encephalitis
B. Herpes encephalitis
C. HIV encephalitis
D. Lewy body disease
E. Rabies encephalitis
Explanation:
The correct answer is E. Rabies is still endemic in many areas of the world, including regions
of Central and South America. The etiologic agent is a virus transmitted to humans by the bite
of a rabid dog or other animal. Exposure to vampire bats (found in Central America) may lead to
infection without a bite. The disease manifests with extraordinary excitability, headache,
aversion to water, convulsions, and coma. In this case, the clinical information provided would
not be sufficient to make a correct choice, but the postmortem finding of elongated
intracytoplasmic neuronal inclusions (Negri bodies) is diagnostic of rabies. Negri bodies are
filled with virus particles and are most often found in the hippocampus and cerebellar cortex.
CMV encephalitis (choice A) affects fetuses (in utero infection) and immunocompromised
patients. The most distinctive microscopic feature is the presence of cytomegalic cells, ie,
abnormally large cells with a large intranuclear purple inclusion and granular basophilic
inclusion in the cytoplasm.
Herpes encephalitis (choice B) could be confused with rabies within the clinical context
provided here, but it is not associated with Negri bodies. It is caused by Herpes simplex virus
type 1 and frequently leads to hemorrhagic necrosis of the temporal lobes.
HIV encephalitis (choice C) is frequently seen in AIDS patients and is due to direct
involvement of the CNS by HIV. Dementia, incontinence, and seizures are frequent
manifestations. Pathologic features in the brain include "microglial nodules," which are
collections of lymphocytes, histiocytes, and microglial cells with variable numbers of
multinucleated giant cells. While microglial nodules are often encountered in viral
encephalitides, multinucleated giant cells are characteristic of HIV encephalitis.
Lewy body disease (choice D) is a dementing disorder characterized clinically by progressive
loss of memory, parkinsonism, and visual/auditory hallucinations, and pathologically by Lewy
bodies (round intracytoplasmic neuronal inclusions that contain alpha-synuclein) in the
substantia nigra and neocortex. The clinical features are obviously different from rabies. Lewy
bodies are also characteristic of Parkinson disease.
A four-month-old child develops cardiac failure and dies three months later. At autopsy, the heart has
no obvious congenital defects, but the cardiac chambers are small and covered with thick, white
endocardium. Histological sections of the heart demonstrate regular bands of elastic tissue in
the thick fibrous endocardium. Which of the following is the most likely diagnosis?
A. Coxsackievirus myocarditis
B. Cardiac amyloidosis
C. Endocardial fibroelastosis
D. Idiopathic subaortic stenosis
E. Loeffler's endocarditis
Explanation:
The correct answer is C. This disease is endocardial fibroelastosis, which is suspected of
being related to intrauterine virus infection, possibly with mumps virus. The endocardium
thickens secondary to a marked increase in fibrous and elastic tissue, which may extend into
the ventricle. The left ventricle is most commonly involved, but other chambers may also be
affected. A variety of other findings may also be present, including mural thrombi, flattened
trabeculae, and abnormal (usually stenosed) valves. The disease occurs in infantile and
adolescent forms.
Coxsackie virus myocarditis (choice A) would produce a flabby myocardium, patchy areas of
hemorrhage, and four chamber dilatation.
In cardiac amyloidosis (choice B), extracellular amyloid deposits would be seen in histological
sections.
Idiopathic subaortic stenosis (choice D) produces a hypertrophic cardiomyopathy.
Loeffler's endocarditis (choice E) is characterized by a prominent eosinophilic infiltrate with
no increase in elastic tissue.
A 75-year-old woman complains to a physician of facial pain, headache, and intermittent visual symptoms.
Both temporal arteries are biopsied. If the biopsies show abnormal vessels, which of the
following would be the most likely pathological finding?
A. Atherosclerotic plaque
B. Fibrinoid necrosis
C. Focal granulomatous inflammation
D. Fungal hyphae
E. Leukocytoclastic vasculitis
Explanation:
The correct answer is C. The suspected disease is temporal arteritis, also known as giant cell
arteritis, because of the focal granulomatous inflammation (with giant cells) that
characterizes the process. The cranial arteries (branches of the carotid system) are most often
involved. Vigorous attempts at diagnosis, which may require biopsying 2-cm lengths of each
temporal artery, are indicated because the process can be patchy. Correct diagnosis is
essential because untreated temporal arteritis can involve the ophthalmic artery, leading to
irreversible blindness.
Atherosclerosis (choice A) is almost never seen in the distal (lower blood pressure) part of
the temporal artery.
Fibrinoid necrosis (choice B) is a feature of polyarteritis nodosa, not temporal arteritis.
Fungal hyphae (choice D) would suggest a fungal infection rather than temporal arteritis.
Leukocytoclastic vasculitis (choice E) is a feature of hypersensitivity angiitis.
A 40-year-old woman has had several episodes of rheumatic fever as a child. She is currently afebrile
and feels well, and has come to a hospital for monitoring echocardiography. Which of the
following would be most likely to be seen in this patient's mitral valve?
A. Ballooning of valve leaflets
B. "Fish mouth" valve
C. Irregular beads of calcification in annulus
D. Large bulky vegetation with adjacent leaflet perforation
E. Tiny vegetations along line of closure of valve leaflet
Explanation:
The correct answer is B. Acute rheumatic fever is a multisystem inflammatory disease that can
follow group A streptococcal pharyngitis. The heart is a primary target of this disease and may
be damaged sufficiently to develop permanent sequelae. The most important of these sequelae is
chronic rheumatic heart disease with valvular damage. The damage most often involves the mitral
and/or aortic valves. The resulting thickened, blunted cardiac valve leaflets, often with
fibrous bridging between valve leaflets and calcification, frequently take on a "fish mouth" or
"button hole" stenotic morphology.
Associate ballooning of valve leaflets (choice A) with mitral valve prolapse.
Associate irregular, beadlike calcifications on the annulus (choice C) with calcification of
the mitral annulus, seen in elderly individuals.
Associate large vegetations and leaflet perforation (choice D) with acute bacterial
endocarditis, which usually involves healthy, rather than previously damaged, valves.
Associate tiny vegetations along line of closure (choice E) with marantic (nonbacterial
thrombotic) endocarditis, most typically seen at autopsy of patients who died after protracted
illness.
A 23-year-old construction worker presents to the emergency room after falling down on his outstretched
right hand. X-ray reveals a fracture of one of the wrist bones. The ER physician is concerned
about the risk for avascular necrosis. Which of the following bones was fractured?
A. Capitate
B. Lunate
C. Pisiform
D. Scaphoid
E. Trapezoid
Explanation:
The correct answer is D. Suspect fracture of the scaphoid (navicular) bone in any young adult
who has "fallen on an outstretched hand" (classic clue). The physician was concerned about the
risk of avascular necrosis because, in some people, the blood supply of the bone is located
distally and a fracture would deprive the proximal region of the bone of its arterial
nourishment. Osteoarthritis is a common complication of scaphoid fractures that do not heal
properly.
The lunate bone (choice B) is commonly dislocated in patients who have fallen on an
outstretched hand. Median nerve injury is a frequently associated occurrence.
The capitate (choice A), pisiform (choice C), and trapezoid (choice E) bones of the wrist are
less commonly associated with falls on an outstretched hand.
A 30-year-old pregnant woman complains to her physician of feeling very tired during her pregnancy. A
complete blood count with differential reveals a hematocrit of 30%, with hypersegmented
neutrophils and large, hypochromic red cells. Deficiency of which of the following would be most
likely to produce these findings?
A. Ascorbic acid
B. Calcium
C. Copper
D. Folate
E. Iron
Explanation:
The correct answer is D. The patient has a megaloblastic anemia, which can be due to deficiency
of folate or B12. Pregnancy increases the need for folate and other nutrients used by both baby
and mother, and may "unmask" a borderline dietary deficiency. For this reason, most
obstetricians recommend vitamin supplements for pregnant women.
Ascorbic acid (choice A) is vitamin C, and its deficiency predisposes for capillary fragility
and oral lesions.
Calcium deficiency (choice B) predisposes for osteoporosis/osteopenia.
Copper deficiency (choice C) is rare; when it occurs, it may cause a hypochromic anemia,
neutropenia, osteoporosis, or hypotonia.
Iron deficiency (choice E) causes a microcytic, hypochromic anemia, with reduced mental and
physical performance.
A 30-year-old female presents to her physician with fever, night sweats, and weight loss. Physical exam
reveals supraclavicular and lower cervical adenopathy. Lymph node biopsy reveals the presence
of Reed-Sternberg cells with lacunae surrounding the nuclei of the cells. Which of the
following variants of Hodgkin's disease is the most likely?
A. Lymphocyte depletion
B. Lymphocyte predominance
C. Mixed cellularity
D. Nodular sclerosis
Explanation:
The correct answer is D. The nodular sclerosis variant of Hodgkin's disease is more common in
women and is associated with the presence of lacunar cells [Reed-Sternberg (RS) cells with
nuclei surrounded by a clear space] and fibrous bands in the lymph nodes. It has a good
prognosis.
Lymphocyte depletion (choice A) is associated with scarcity of lymphocytes, multiple RS cells,
fibrosis, and necrosis. It has a poor prognosis.
Lymphocyte predominance (choice B) is the least common form of Hodgkin's. It is associated with
an abundance of lymphocytes and histiocytes and scant RS cells.
Mixed cellularity (choice C) is the most common form of Hodgkin's. It is associated with the
presence of neutrophils, lymphocytes, eosinophils, plasma cells, and histiocytes. Many classic
RS cells may be identified.
Examination of a peripheral blood smear demonstrates a leukemia composed of small mature lymphocytes
without blast forms. Which of the following is the most likely age of this patient?
A. 1 year
B. 5 years
C. 20 years
D. 45 years
E. 65 years
Explanation:
The correct answer is E. Different leukemias tend to affect populations of different ages. The
disease described is chronic lymphocytic leukemia (CLL), which is a disease of older adults.
Both the one year-old (choice A) and the five year-old (choice B) would be most likely to have
acute lymphocytic leukemia (ALL).
The 20 year-old (choice C) would be most likely to have acute myelocytic leukemia (AML).
The 45 year-old (choice D) would be likely to have either AML or chronic myelogenous leukemia
(CML).
A 10-year-old boy has a small tumor in the wall of the right lateral ventricle. A biopsy of this tumor
is consistent with subependymal giant cell astrocytoma. Which of the following lesions may also
be present in this patient?
A. Café-au-lait spots
B. Cortical tubers
C. Hemangioblastoma
D. Lisch nodules
E. Schwannoma of the 8th cranial nerve
Explanation:
The correct answer is B. This item tests your knowledge of neurocutaneous syndromes, a group of
hereditary conditions characterized by concomitant neoplastic or hamartomatous lesions
predominantly affecting the skin and nervous system. Subependymal giant cell astrocytoma is a
peculiar astrocytic tumor that grows from the walls of the lateral ventricles. It is
pathognomonic of tuberous sclerosis, which is caused by mutations of TS1 or TS2 genes. Tuberous
sclerosis manifests with multiple hamartomatous lesions in the skin, CNS, and visceral organs.
Cortical tubers are malformed (hamartomatous) nodules of the cortex, probably resulting from
faulty cortical development. Other lesions include shagreen patches and ash-leaf spots on the
skin, cardiac myomas, and renal angiomyolipomas.
Café-au-lait spots (choice A) are found in both types of neurofibromatosis. Lisch nodules
(choice D) are small pigmented nodular lesions of hamartomatous nature that are present in the
iris of patients with neurofibromatosis type 1. Schwannomas of the 8th cranial nerve (choice
E), especially when bilateral, are typically associated with neurofibromatosis type 2.
Hemangioblastoma (choice C) is a vascular tumor of unknown histologic origin that frequently
develops in the cerebellum of patients with von Hippel-Lindau syndrome. Renal cell carcinomas
are also common in this disease. Von Hippel-Lindau syndrome is caused by autosomal dominant
mutations of the VHL gene, a tumor suppressor gene. You may recall that mutations of VHL gene
are also found in the majority of sporadic renal cell carcinomas.
A 70-year-old male patient dies with severe dementia. Autopsy demonstrates marked atrophy of the frontal
and temporal lobes, with relative sparing of the rest of the brain. Which of the following
microscopic features would be most useful in establishing the diagnosis?
A. Enlarged presynaptic axon terminals surrounding a central core of extracellular
amyloid-like substance
B. Intracytoplasmic spherules composed of paired helical filaments
C. Intracytoplasmic spherules that stain brightly eosinophilic
D. Intranuclear and intracytoplasmic inclusion bodies in enlarged cells
E. Small cytoplasmic vacuoles containing a central granule
Explanation:
The correct answer is B. Selective frontal and temporal atrophy in a demented patient suggests
Pick's disease. Microscopically, severe neuronal loss and astrocytosis are seen. The
characteristic microscopic finding in this disorder is the presence of Pick's bodies, which are
intracytoplasmic spherules composed of paired helical filaments, seen best with silver stains.
Choice A describes senile plaques. These are seen in Alzheimer disease as well as in some
normal elderly individuals.
Choice C describes Lewy bodies, seen in Parkinson's disease.
Choice D describes the inclusion bodies typically seen in glial cells and endothelial cells in
cytomegalovirus encephalopathy.
Choice E describes granulovacuolar degeneration.
A 30-year-old female is diagnosed with cervical intraepithelial neoplasia associated with a previous
viral infection. Which of the following viral products are implicated in producing this type of
dysplasia?
A. EBNA proteins
B. E1A and E1B proteins
C. E6 and E7 proteins
D. Large tumor antigen
Explanation:
The correct answer is C. Cervical intraepithelial neoplasia (CIN) is associated with human
papilloma virus (HPV) infection, particularly types 16 or 18. These papillomaviruses produce E6
and E7 proteins, which induce the expression of cellular p53 and p110Rb oncogenes,
respectively.
EBNA proteins (choice A) are produced by the Epstein-Barr virus and are associated with
hepatocellular carcinoma, Burkitt's lymphoma, and carcinoma of the nasopharynx.
E1A and E1B proteins (choice B) are produced by adenoviruses 12, 18, and 31. They also bind to
the p53 and p110Rb oncogenes, respectively.
Large tumor antigen (choice D) is produced by simian virus 40 (SV40), a papovavirus found in
monkeys that is known to produce sarcoma in laboratory hamsters.
A 10-year-old child develops a testicular mass and undergoes orchiectomy. On cut section, the mass shows
a variety of appearances and colors. Histologically, many different tissues are seen, including
cartilage, thyroid, and neural tissue. A small focus of clear-cut squamous cell carcinoma is
seen. Which of the following is the most appropriate classification for this tumor?
A. Dermoid cyst
B. Embryonal carcinoma
C. Immature teratoma
D. Solid mature teratoma
E. Teratoma with malignant transformation
Explanation:
The correct answer is E. This is teratoma with malignant transformation. The possibility of
malignant transformation is why even obvious mature teratomas with very well differentiated
tissues should be completely excised. Malignant transformation is more common in teratomas in
adults than in children or babies.
Dermoid cyst (choice A) is a cystic form of mature teratoma, usually found in the ovaries.
Embryonal carcinoma (choice B) is a type of adenocarcinoma rather than squamous cell carcinoma.
Immature teratoma (choice C), while clinically malignant, shows embryonal tissues and often
displays no clear-cut cytological evidence of malignancy.
Solid mature teratoma (choice D) without the added descriptor "with malignant transformation"
is by definition a benign tumor. Careful extensive sampling is required to exclude minute foci
of cancerous transformation.
An infant is evaluated for partial intestinal obstruction that has been present from birth.
Esophagogastroduodenal endoscopic visualization fails to demonstrate an intraluminal lesion, but
does show prominent narrowing at the level of the mid duodenum. CT studies demonstrate a mass
lesion surrounding that portion of the duodenum. Which type of tissue is most likely present
within the lesion?
A. Gastric
B. Hepatic
C. Pancreatic
D. Renal
E. Small intestinal
Explanation:
The correct answer is C. The lesion is an annular pancreas, which is a rare pancreatic
malformation, in which the pancreatic head encircles the second part of the duodenum,
potentially causing obstruction.
An increase in thickness of the muscular part of the gastric wall (choice A) can cause
congenital pyloric stenosis.
While the liver is near the first and second parts of the duodenum, there is no common
developmental anomaly in which hepatic tissue (choice B) would surround the duodenum.
The kidneys (choice D) are located retroperitoneally and relatively far lateral from the
duodenum, and would not be expected to surround it.
Duplication or atresia of the duodenum itself (choice E) can occur, but would not cause the
appearance of a mass surrounding the duodenum.
A 65-year-old male with a history of smoking and alcohol abuse complains of poor appetite and difficulty
swallowing both solid and liquid foods over the course of the last 4 months. He has lost 20 lbs
and occasionally vomits blood. A mass is detected in his esophagus and is subsequently
biopsied. What is the most likely histological appearance of the biopsy?
A. Glandular epithelium associated with desmoplasia
B. Malignant tumor of mesenchymal origin
C. Squamous cell morphology
D. Tumor derived from all three germ layers
E. Tumor of epithelial origin demonstrating transitional cell morphology
Explanation:
The correct answer is C. The most common esophageal cancer is squamous cell in origin. Recall
that the esophageal mucosa consists of stratified, nonkeratinized, squamous epithelium. Smoking
and alcohol increase the risk for the development of esophageal carcinoma. Suspect cancer when
there are signs like rapid weight loss in a short period of time and symptoms such as
dysphasia, hematemesis, and anorexia.
Glandular epithelium (choice A) is associated with adenocarcinoma, which is often associated
with Barrett's esophagus. This is not as common as squamous cell carcinoma.
A mesenchymal tumor (choice B) is a sarcoma.
A teratoma can be derived from all three germ layers (choice D), e.g., a dermoid cyst in the
ovary.
Transitional cell morphology (choice E) is found in the urinary system and not in the
esophagus, unless it was metastatic to that location.
A 45-year-old woman has crippling arthritis of her fingers, wrists, and knees. Physical examination
demonstrates large subcutaneous nodules near the patient's elbows. Serology demonstrates a
positive rheumatoid factor. The patient's probable disease has the strongest association with
which HLA type?
A. HLA-A3
B. HLA-B27
C. HLA-DR2
D. HLA-DR3
E. HLA-DR4
Explanation:
The correct answer is E. The disease is rheumatoid arthritis, which commonly presents as
described in the question stem. Rheumatoid nodules develop in 20 to 30 percent of patients,
usually on or around joints, on extensor surfaces, or on other areas subjected to mechanical
trauma. RF stands for rheumatoid factor, and is actually anti-self IgG (usually IgM). The most
important HLA association is with HLA-DR4.
Associate HLA-A3 (choice A) with primary hemochromatosis.
Associate HLA-B27 (choice B) with psoriasis, ankylosing spondylitis, inflammatory bowel
disease, and Reiter's syndrome.
Associate HLA-DR2 (choice C) with systemic lupus erythematosus (also associated with HLA-DR3,
choice D).
Also, associate HLA-DR3 (choice D) with Type I diabetes (which has a second association with
HLA-DR4).
Which of the following is the most common site for development of embryonal rhabdomyosarcoma?
A. Gastrointestinal tract
B. Head and neck
C. Kidneys
D. Liver
E. Lungs
Explanation:
The correct answer is B. Embryonal rhabdomyosarcoma is the most common form of
rhabdomyosarcoma. The tumor is composed predominantly of small, round cells resembling cells
found in developing muscle. The head and neck (particularly the nose, nasopharynx, and orbit)
is the most common site for the development of embryonal rhabdomyosarcoma. Other favored sites
are the genitourinary tract (e.g., sarcoma botyroides, or embryonal rhabdomyosarcoma of the
vagina) and the extremities.
A 32-year-old woman presents with complaints of several months of burning substernal chest pain
exacerbated by large meals, cigarettes, and caffeine. Her symptoms are worse when she lies on
her back, especially when sleeping at night. Antacids often improve her symptoms. This patient
is at risk for which of the following conditions?
A. Cardiac ischemia
B. Columnar metaplasia of the distal esophagus
C. Mallory-Weiss lesion in the esophagus
D. Squamous cell carcinoma
E. Zenker's diverticulum
Explanation:
The correct answer is B. This woman likely suffers from reflux esophagitis, a condition in
which the lower esophageal sphincter (LES) does not adequately prevent acidic gastric contents
from refluxing back into the distal esophagus. Most commonly, there is a defect in the LES
mechanism itself, in addition to secondary causes such as pregnancy (due to increased abdominal
pressure) and some medications (anticholinergics, beta-2 agonists, theophylline, nitrates,
calcium-channel blockers). Symptoms can mimic cardiac chest pain and must be carefully
evaluated. Complications of reflux esophagitis include esophageal strictures, ulcerations,
laryngitis, pulmonary aspiration, and Barrett's esophagus (columnar metaplasia of the distal
esophagus). Barrett's esophagus is considered a premalignant state, with roughly a 30-fold
increase in the incidence of esophageal adenocarcinoma. The normal squamous epithelium of the
esophagus transforms into columnar epithelium similar to gastric epithelium as a result of
recurrent reflux of acidic gastric contents.
Anginal pain, signaling cardiac ischemia (choice A), is generally not burning in nature, and is
not relieved by antacids.
Mallory-Weiss lesions (choice C) are actual tears of the epithelia of the proximal stomach or
distal esophagus as a result of retching (seen in anorexics and alcoholics).
The incidence of pure squamous cell carcinoma (choice D) is not increased by acid reflux
disease.
Zenker's diverticula (choice E), the most common of esophageal diverticuli, are not true
diverticuli, but only mucosal herniations that can cause obstructive symptomatology.
A 70-year-old man presents with severe acute abdominal pain. Physical examination reveals tenderness
with guarding localized to the left lower quadrant. A complete blood count with differential
shows a white count of 18,000/mm3 with increased neutrophil band forms. Paracentesis
demonstrates mixed flora bacteria with many neutrophils in the peritoneal fluid. Which of the
following is the most probable source of the infection?
A. Bladder infection
B. Colonic diverticulum
C. Prostatic inflammation
D. Ruptured appendix
E. Ureteral stone
Explanation:
The correct answer is B. Diverticula that become impacted with fecaliths (undigested food
residues) can become inflamed and perforate, causing the equivalent of appendicitis, but
typically involve the left rather than right lower quadrant. This complication of
diverticulitis can produce acute peritonitis, evidenced by the abdominal tenderness, guarding,
and leukocytosis, and can kill elderly debilitated patients. Diagnostic paracentesis may be
valuable in determining if perforation has occurred.
Bladder infection (choice A), usually related to an enlarged prostate, is common in elderly
men, but does not usually cause peritonitis.
Prostatic inflammation (choice C) or infection does not usually spread to the abdomen.
Acute appendicitis (choice D) is usually a disease of young adults and is characterized by
tenderness in the right lower quadrant.
Ureteral stones (choice E) can cause severe abdominal pain but do not usually cause
peritonitis.
A 25-year-old woman develops extensive pruritic wheals following ingestion of seafood to which she was
allergic. While these lesions are usually not biopsied, a biopsy would probably show which of
the following features?
A. Dilated superficial lymphatic channels
B. Granular complement and IgG at dermal/epidermal junction
C. Microscopic blisters
D. Munro microabscesses
E. Solar elastosis
Explanation:
The correct answer is A. Urticaria (hives) are pruritic wheals that form after mast cells
degranulate and trigger localized dermal edema with dilated superficial lymphatic channels. The
mast cell degranulation is sometimes, but not always, triggered by IgE-antigen interactions.
Granular complement and IgG deposition at the dermal/epidermal junction (choice B) is a
characteristic of systemic lupus erythematosus.
Microscopic blisters (choice C) are a characteristic of dermatitis herpetiformis.
Munro abscesses (choice D) are a characteristic of psoriasis.
Solar elastosis (choice E) is found in actinic keratoses.
A 54-year-old African-American female patient undergoes a routine insurance physical examination. Chest
x-ray reveals bilateral hilar masses. Biopsy of the masses shows granulomata, but acid-fast and
fungal stains are negative for organisms. Which of the following diseases should be suspected?
A. Caroli's disease
B. Raynaud's disease
C. Sarcoidosis
D. Scleroderma
E. Systemic lupus erythematosus
Explanation:
The correct answer is C. Sarcoidosis is a multisystem disease characterized by non-caseating
granulomata in a variety of organs. The disease may be symptomatic (respiratory and
constitutional symptoms) or may be discovered incidentally when chest x-ray or autopsy reveals
bilateral hilar adenopathy. Definitive diagnosis is based on biopsy, which reveals noncaseating granulomata that are negative for fungi or acid-fast bacilli. Sarcoidosis is more
common in individuals of African descent.
Caroli's disease (choice A) is a congenital malformation of the bile duct system.
Raynaud's disease (choice B) is a vasospasm of vessels that causes temporary ischemia in the
hands.
Scleroderma (choice D), or progressive systemic sclerosis, is characterized by progressive
fibrosis of skin and internal organs.
Systemic lupus erythematosus (choice E) is an autoimmune disease characterized by vasculitis
(which may produce a variety of symptoms depending on the site of the lesion), rash, renal
disease, hemolytic anemia, and neurologic disturbances.