Case 10 (ML, SH, JC)
The patient was a 3-year-old male who presented with a 4-day history of fevers. He became acutely ill and
vomited during lunch. Over the next 4 days he developed fevers as high as
40°C that were controlled by Tylenol. He also developed cough, rhinorrhea, and conjunctivitis. He appeared to
be fatigued, and his parents reported that he was “very sleepy.” Over the past 2 days, his eyes had begun to itch
and were painful. His parents noted that his eyes were puffy and he was sensitive to light. He had had no rashes.
The patient’s lips were dried and cracked, and he had a greatly reduced urinary output.
Other history pertinent to his illness is that he attended preschool twice per week, where he had multiple sick
contacts (his illness occurred in late January). His 1-year old sibling had otitis media, some wheezing, vomiting,
and a productive cough.
On physical examination he had a temperature of 38.6°C, pulse rate of 126 beats/min, and respiratory rate of
28/min with an oxygen saturation of 100% on room air. Significant findings included bilateral conjunctivitis
with exudate in the left eye, bleeding, cracked lips, and rhinorrhea. He had shotty lymphadenopathy but no rash.
His feet were slightly edematous. His respiratory examination was normal. Laboratory findings were all normal.
A nasopharyngeal swab was sent for rapid antigen testing
1. What is the agent causing his infection? ‘What symptoms does he have which are consistent with his
illness? What are the key virulence factors of this agent?
2. What is the usual outcome of this infection in this patient population? What patient populations are
particular prone to infections with this
agent?
3. What will you tell the patient/parents?
Case 61(DM, CS, YV)
The patient was a 21-year-old male who presented with complaints of nausea, vomiting, diffuse body aches,
productive cough, fever, and loose, watery diarrhea. He had not urinated in the prior 24 hours and complained of
dizziness on standing. He denied headache or abdominal pain. His past medical history was significant for sore
throat 3 weeks previously. He also reported that he had a urinary tract infection “a month or two” ago. He
received intravenous fluids, and a fecal specimen was sent for culture and ova and parasites. The stool specimen
was positive for Entamoeba histolytica (or Entamoeba dispar). At that point, one day into his hospitalization,
the infectious disease (ID) service was consulted.
The patient was from North Carolina, had no recent travel history, drank alcohol, and denied sexual contact. On
physical examination by the ID fellow, the patient was found to have a fever of 3 9.1°C, a heart rate of 104/min,
and blood pressure of 134/84 mm Hg. His physical examination revealed enlarged tonsils but no cervical,
axillary or inguinal adenopathy. No hepatosplenomegaly was noted. Bowel sounds were normal. Chest was
clear on auscultation and by chest radiograph. Laboratory studies were significant for a white blood cell count of
2,200 with 57% polymorphonuclear leukocytes, 33% lymphocytes, and 6% atypical lymphocytes. Aspartate
aminotransferase (AST) was 650 U/liter, alanine aminotransferase (ALT) was 830 U/liter, and lactate
dehydrogenase (LDH) was 1,000 U/liter. Hepatitis A, B, and C virus and HTV serologic test results were
negative. The etiologic agent of his primary illness was detected by culture, positive antigen test, and PCR
(polymerase chain reaction). E. histolytica was a secondary infection.
1. This patient has two infections. One, with E. histolytica, explains the occurrence of nausea, vomiting,
diarrhea, and dehydration. However, infection with this organism does not explain his sore throat 3 weeks
prior to his hospitalization, the tonsillar enlargement, his systemic complaints of fever, nausea, vomiting,
and diffuse body aches, or the laboratory findings of atypical lymphocytes and hepatitis. With what
syndrome seen in young adults are these findings consistent? What are the viral etiologies of this condition?
2. What is his specific diagnosis? Explain why serologic testing for antibody was negative at this stage of his
infection, but the pathogen was identified by antigen testing, PCR, and culture. What clues were present in
his history that suggested the possibility of this pathogen?
3.
What populations are at increased risk for infection with this agent?
4.
Describe the pathogenesis of his infection which resulted in the mono-like illness. What is the natural
history of this infection?
5.
His E. histolytica infection was successfully treated. How should this patient be managed for the other
infection?
6. What will you tell the patient/parents?
Case 63 (RM, MI, PS)
The patient was an 8-year-old male with a 2-day history of diarrhea. He presented with worsening diarrhea (14
movements that day) which had become bloody. He also complained of pain on defecation. He had vomited
once. He had attended a cookout 6 days previously. He claimed that his mother made him eat a hamburger that
was “pink inside” even though “he did not like it.” His physical examination was benign except for obvious
dehydration. His laboratory findings were significant for a white blood cell count of 13,100/l with 9,700
neutrophils/l, a methylene blue stain of feces that showed abundant polyrnorphonuclear cells, and a positive
stool guaiac. He was treated with trimethoprim-sulfamethoxazole and intravenous fluid therapy for dehydration.
He quickly improved and was discharged within 24 hours. Culture of his stool specimen on MacConkey-sorbitol
agar is shown in Fig. 1.
1. What is the most likely etiologic agent of his infection? What two important clues are found in this case that
helped you determine the etiology of his infection?
2. What are the major virulence factors produced by this organism? How do they act and what are their roles in
the pathogenesis of disease?
3. Why are these organisms so difficult to detect in feces? Think about one of the major virulence factors
produced by this organism and how it is encoded genetically.
4. Besides cultures, what other methods may prove useful for detecting this organism? Explain how these
methods could be used to detect this organism. Why might such methods be of value in studying outbreaks
of disease with this organism?
5. How is the organism usually spread? How can infection with this organism be prevented?
6. Was using antibiotic therapy in this patient an appropriate clinical decision?
7. What are sequelae associated with this infection? What organ and cell types are specifically targeted? What
is the outcome of these sequelae?
8. What will you tell the patient/parents?
Figure 1
Case 64 (LR, SI, BB)
A 30-year-old woman presented to the clinic with fever, back ache and headache of 2 days’ duration. She
complained bitterly about intense myalgias in the upper arms and pain on moving her eyes. She had just
returned from a trip to El Salvador, where she had extensive exposure to mosquitoes. On physical examination,
she appeared uncomfortable but not toxic. A blanching, erythematous rash was present on the face, arms, trunk,
and thighs (Fig. 1). There was no enanthem, murmur, or splenomegaly. Her white blood cell count was l,600/l
with a normal differential, platelet count was l40,000/l, and hemoglobin was 17.5 g/dl. Convalescent-phase
antibodies to a mosquito-borne viral disease were diagnostic.
1. What viral disease did the patient acquire? By what type of mosquitoes is this virus transmitted? Are any of
these mosquitoes found in the United States?
2. Severe disease, which can be fatal, can occur with this infection. What are the clinical manifestations of
severe disease as a result of infection with this virus?
3. There are four distinct serotypes of this virus. Would you predict that infection with one serotype would
confer immunity to the other serotypes?
4. In what geographic range is this disease endemic? ‘What means can be taken by travelers to endemic
regions to prevent infection?
5. What will you tell the patient/parents?
Figure 1
Case 68 (MD, SK, JL)
The patient was a 54-year-old male retired U.S. Air Force pilot. He was in excellent health until he developed a
chronic neurologic disorder that led to his death 6 months after the onset of symptoms. The initial manifestations
were nonspecific: forgetfulness, subtle behavioral changes, headaches, and fatigue. Disequilibrium, a widebased gait, and double vision developed, and he sought medical attention. There was no history of alcohol use or
a tick bite. He was never febrile. He was treated with penicillin and tetracycline for presumed Lyme disease or
Rocky Mountain spotted fever (RMSF). His symptoms persisted. Serology tests for Borrelia burgdorferi and
RMSF were negative. Evaluation by a neurologist revealed findings consistent with cerebellar and brainstem
degeneration. Head computed tomogram (CT) scan revealed mild cerebral and cerebellar atrophy but no mass
lesions. His social history was significant for having been an air force pilot for 23 years. He spent several years
in Guam and Vietnam. His eating habits were conventional. He had never been transfused, and he had no known
risk factors for HW.
Routine hematology and chemistry laboratory tests were normal; HIV and VDRL (Venereal Disease Research
Laboratory) tests were negative. Lumbar puncture revealed a normal opening pressure, and all tests on
cerebrospinal fluid, including cultures, were within normal limits. No brain biopsy was done.
He had a progressive decline in his neurologic status and died. An autopsy was done and the neuropathologic
exam was pathognomonic for this patient’s diagnosis. Extensive spongiform changes were prominent in the
cerebrum, cerebellum, and basal ganglia (Fig. 1).
1. What viruses can cause chronic neurologic disorders?
2. The etiology in this particular case is an unconventional agent that causes a noninflammatory subacute
degenerative neurologic disorder. What is the name of the etiologic agent? What is the disease in humans
called?
3. A similar disease occurs in sheep. What is it?
4. What is the disease called in cattle? Describe an ongoing epidemic in cattle that has been associated with a
variant of this disease in humans.
5. Name three possible modes of person-to-person transmission of this agent.
6. What will you tell the patient/parents?
Figure 1