PATHOLOGY REVIEWER
LONG EXAM 2
Virus / Causative
Agent
Disease
INFECTIOUS DISEASES
Mode of Transmission
Signs & Symptoms
Histologic and Gross Findings
Acute (Transient) Viral Infections
Measles virus
(Paramyxoviridae,
genus Morbillivirus)
Measles (Rubeola)
Respiratory droplets
High fever, cough, coryza, conjunctivitis, Koplik spots,
maculopapular rash spreading from face downward
Warthin–Finkeldey giant cells (multinucleated
cells) in lymphoid tissue; hyperplastic lymphoid
follicles; rash due to T-cell–mediated vasculitis
Mumps virus
(Paramyxoviridae,
genus Rubulavirus)
Mumps
Respiratory droplets,
saliva
Parotitis (painful swelling of parotid glands), orchitis, meningitis,
pancreatitis
Edematous parotid glands with lymphocytic
infiltrates; interstitial orchitis with germ cell loss
Dengue virus
(Flavivirus, RNA virus)
Dengue fever / Dengue
hemorrhagic fever
Mosquito bite (Aedes
aegypti)
Sudden high fever, severe headache, myalgia (“breakbone fever”),
rash, bleeding tendencies, plasma leakage
Capillary leak with hemorrhages; liver shows
midzonal necrosis; bone marrow suppression;
petechiae on skin
Latent Viral Infections
Herpes simplex virus
type 1 (HSV-1)
Oral herpes (labialis),
encephalitis
Direct contact with
lesions, saliva
Painful vesicles on lips/mouth, recurrence triggered by stress or
fever
Intranuclear Cowdry type A inclusions,
multinucleated giant cells; ballooning degeneration
of infected cells
Herpes simplex virus
type 2 (HSV-2)
Genital herpes
Sexual contact, vertical
(perinatal)
Painful vesicular genital lesions, dysuria, recurrent episodes
Same as HSV-1 (Cowdry A inclusions,
multinucleated cells); vesicular ulceration of
mucosa
Varicella-zoster virus
(VZV)
Chickenpox (primary),
Shingles (reactivation)
Respiratory droplets
(primary), contact with
lesions (reactivation)
Vesicular rash (“dew drops on rose petals”), dermatomal vesicles
in shingles
Multinucleated giant cells with intranuclear
inclusions, necrotic keratinocytes; ganglionitis in
latent stage
Cytomegalovirus (CMV)
CMV infection /
mononucleosis-like
illness / congenital
CMV
Body fluids,
transplacental,
transfusion, organ
transplant
Often asymptomatic; may cause hepatitis, pneumonitis, or
congenital malformations
“Owl’s eye” intranuclear inclusions in infected
cells; cytomegaly; necrosis in affected organs
Transforming (Oncogenic) Viral Infections
Epstein–Barr virus
(EBV)
Infectious
mononucleosis;
associated cancers
(Burkitt lymphoma,
nasopharyngeal
carcinoma, Hodgkin
lymphoma)
Saliva (“kissing disease”)
Fever, sore throat, lymphadenopathy, splenomegaly, atypical
lymphocytosis
Atypical lymphocytes (Downey cells) in blood;
reactive hyperplasia of lymphoid tissue; in
malignancy—monomorphic B-cell proliferation
PATHOLOGY REVIEWER
LONG EXAM 2
Bacteria /
Causative Agent
INFECTIOUS DISEASES
Disease
Mode of Transmission
Signs & Symptoms
Histologic & Gross Findings
Gram-positive Bacteria
Staphylococcus
aureus
Pyogenic skin and soft tissue infections:
• Furuncle (boil) – localized suppurative
inflammation of hair follicle forming a painful
nodule
• Carbuncle – confluent deep abscesses of
several adjacent hair follicles, may cause
fever/systemic toxicity
• Hidradenitis suppurativa – chronic, recurrent
suppurative infection of apocrine glands
(axilla/groin)
• Paronychia – infection around the nail bed
• Bullous impetigo – superficial vesiculobullous
lesions caused by exfoliative toxin
• Staphylococcal scalded skin syndrome (SSSS) –
widespread epidermal sloughing due to exfoliative
toxin
Direct contact, fomites,
contaminated food
Painful nodules or abscesses,
fever; in SSSS – fever, diffuse
erythema, exfoliation; in impetigo –
superficial honey-colored crusted
lesions
Suppurative inflammation, abscess formation;
intraepidermal cleavage (SSSS) at granular layer;
necrosis in deeper lesions
Subdermal edema prominent in abscesses and
cellulitis
Streptococcus
pyogenes (Group A)
Pharyngitis, impetigo, erysipelas, scarlet fever,
cellulitis
Respiratory droplets, skin
contact
Sore throat, rash, strawberry
tongue; erysipelas – sharply
demarcated erythema with warmth
and tenderness
Suppurative inflammation, fibrinoid necrosis of
small vessels (rheumatic lesions)
Subdermal edema in erysipelas and cellulitis
Streptococcus
pneumoniae
Lobar pneumonia, meningitis
Respiratory droplets
Fever, productive cough with rusty
sputum, pleuritic chest pain
Lobar consolidation (red → gray hepatization),
alveoli with neutrophils and fibrin
Enterococcus
faecalis/faecium
UTI, endocarditis, wound infections
Fecal contamination,
nosocomial
Dysuria, fever, sepsis
Abscess formation with neutrophils
Corynebacterium
diphtheriae
Diphtheria
Respiratory droplets
Sore throat, low-grade fever,
grayish pseudomembrane in
throat, myocarditis
Coagulative necrosis with fibrinopurulent
pseudomembrane; inflammatory exudate
Mild subepithelial edema in mucosa
Bacillus anthracis
Anthrax (cutaneous, inhalational, gastrointestinal)
Contact with infected
animals/products,
inhalation of spores
Cutaneous: black eschar with
massive edema; Inhalational:
dyspnea, widened mediastinum
Serosanguinous hemorrhage, necrosis, “boxcar”
bacilli
Massive subepidermal and subdermal edema
(gelatinous)
Nocardia asteroides
Nocardiosis (pulmonary, cutaneous, CNS)
Inhalation or inoculation
from soil
Chronic pneumonia, draining
cutaneous sinuses
Suppurative granulomas with filamentous, weakly
acid-fast bacteria
Variable subdermal edema in cutaneous form
PATHOLOGY REVIEWER
LONG EXAM 2
Bacteria / Causative
Agent
INFECTIOUS DISEASES
Disease
Mode of Transmission
Signs & Symptoms
Histologic & Gross Findings
Gram-negative Bacteria
Neisseria meningitidis
Meningococcal meningitis
Waterhouse-Friderichsen Syndrome (bilateral
adrenal hemorrhage)
Respiratory droplets
Fever, headache, neck stiffness,
petechial rash
Neutrophilic meningitis, hemorrhagic adrenalitis
Possible subdermal hemorrhage/petechiae
Neisseria
gonorrhoeae
Gonorrhea
Sexual contact
Purulent genital discharge,
dysuria, "morning drop"
Suppurative inflammation, neutrophilic exudate
Subepithelial edema in mucosa
Necrosis of bronchial epithelium, peribronchial
lymphocytes
Bacilli entangle with cilia of the bronchial epithelial
cells
Bordetella pertussis
Whooping cough (Pertussis)
Respiratory droplets
Paroxysmal cough, inspiratory
“whoop”, lymphocytosis
Pseudomonas
aeruginosa
Opportunistic infections (burns, wounds,
pneumonia, sepsis)
Contact with
contaminated water,
hospital equipment
Greenish pus, fruity odor, fever,
sepsis
Bacilli forming a perivascular blue haze with
thrombosis
Necrotizing inflammation, vascular invasion,
ecthyma gangrenosum lesions
Subdermal edema with hemorrhage and necrosis
Haemophilus ducreyi
Chancroid (soft chancre)
Sexual contact
Painful genital ulcers, tender
lymphadenopathy
Ulcers with necrotic base, suppurative exudate
Subepidermal edema around ulcer margins
Klebsiella
granulomatis
(Calymmatobacterium
granulomatis)
Granuloma inguinale (Donovanosis)
Sexual contact
Painless, beefy-red genital ulcers,
bleed easily
Granulomatous inflammation, Donovan bodies in
macrophages
Psedoepitheliomatous hyperplasia
safety pin-shaped organism
Mycobacterium
tuberculosis
Tuberculosis (pulmonary or extrapulmonary)
Airborne droplets
Chronic cough, hemoptysis, fever,
weight loss
Caseating granulomas, Langhans giant cells,
cavitary lesions
fibrosis predominates
Mycobacterium
avium–intracellulare
complex (MAC)
Disseminated infection (esp. in
immunocompromised)
Inhalation or ingestion
Fever, weight loss, diarrhea
(AIDS)
Foamy macrophages packed with acid-fast bacilli
Mild interstitial edema
Mycobacterium
leprae
Leprosy (Hansen’s disease)
Prolonged contact, nasal
secretions
Hypopigmented anesthetic
patches, thickened nerves
Tuberculoid: granulomas with giant cells;
Lepromatous: foamy macrophages (Virchow cells)
Localized dermal edema possible in lesions
PATHOLOGY REVIEWER
LONG EXAM 2
Bacteria / Causative Agent
INFECTIOUS DISEASES
Disease / Stages
Mode of Transmission
Signs & Symptoms
Histologic & Gross Findings
Spirochetes
Primary Syphilis
Sexual contact
Painless indurated ulcer (chancre) at
inoculation site; often on genitals or
oral mucosa; regional
lymphadenopathy
Endarteritis obliterans with dense plasma cell and
lymphocytic infiltrate; spirochetes visible on darkfield microscopy or silver stain
Secondary Syphilis
Systemic dissemination
(via blood)
Maculopapular rash including palms
and soles, condyloma lata (moist, flat
papules), mucous patches,
lymphadenopathy, fever, malaise
Proliferative endarteritis, lymphoplasmacytic
infiltrate, mucocutaneous lesions teeming with
spirochetes
Tertiary Syphilis
Reactivation after latency
Gummatous lesions in skin, bone,
liver; aortitis → aneurysm;
neurosyphilis (tabes dorsalis, general
paresis)
Granulomatous inflammation with central
necrosis (gumma), obliterative endarteritis of
vasa vasorum
Congenital Syphilis
Transplacental (vertical)
Stillbirth or neonatal disease; snuffles
(nasal discharge), rash, skeletal
deformities (saber shins),
Hutchinson’s triad (keratitis, notched
incisors, deafness)
Fibrosis and necrosis in multiple organs;
inflammation of cartilage and periosteum;
spirochetes in tissues (Warthin-Starry stain)
Lyme Disease
Stage I (Early localized): Erythema
migrans (“bull’s-eye” rash), flu-like
symptoms
Stage II (Early disseminated):
Secondary lesions, carditis, migratory
arthralgias, cranial nerve palsy (esp. CN
VII)
Stage III (Late): Chronic arthritis,
encephalopathy, acrodermatitis chronica
atrophicans
Tick bite (Ixodes species)
Expanding erythematous rash,
neurologic and cardiac symptoms,
later arthritis
Perivascular lymphocytic and plasma cell
infiltrates, chronic synovitis, spirochetes on
silver stain
Treponema pallidum
Borrelia burgdorferi
Anaerobic Bacteria (Clostridial Infections)
Clostridium perfringens
Gas gangrene (clostridial myonecrosis),
food poisoning
Wound contamination
(spores), ingestion of
contaminated food
Rapidly progressive tissue necrosis,
gas bubbles, foul odor, crepitus
Myonecrosis, gas formation in tissues, Grampositive rods without neutrophils due to toxinmediated necrosis
Clostridium tetani
Tetanus
Wound contamination
(soil spores)
Trismus (lockjaw), risus sardonicus,
generalized muscle spasms
No major histologic change; toxin blocks inhibitory
neurotransmitters (GABA, glycine) in CNS
Clostridium botulinum
Botulism
Ingestion of preformed
toxin (canned foods),
wound contamination
Flaccid paralysis, diplopia,
dysphagia, respiratory failure
Toxin prevents acetylcholine release at
neuromuscular junction; no significant lesion
histologically
Clostridium difficile
Pseudomembranous colitis
Antibiotic therapy (alters
gut flora)
Watery diarrhea, fever, abdominal
pain
Pseudomembranes on colonic mucosa (necrotic
debris, fibrin, neutrophils, mucus)
PATHOLOGY REVIEWER
LONG EXAM 2
Bacteria / Causative
Agent
INFECTIOUS DISEASES
Disease / Stages
Mode of Transmission
Signs & Symptoms
Histologic & Gross Findings
Obligate Intracellular Bacteria
Chlamydia trachomatis
Trachoma, inclusion conjunctivitis,
nongonococcal urethritis, cervicitis, PID,
lymphogranuloma venereum (LGV)
Sexual contact, perinatal,
fomites (for trachoma)
Chronic conjunctivitis (trachoma →
blindness), urethritis, cervicitis, painful
inguinal lymphadenopathy (LGV)
Cytoplasmic inclusion bodies (elementary +
reticulate bodies); granulomatous inflammation
(LGV)
Chlamydophila
pneumoniae / psittaci
Atypical pneumonia, psittacosis (bird exposure)
Aerosolized droplets
Mild pneumonia, cough, fever,
headache
Interstitial pneumonitis with lymphocytes and
plasma cells; cytoplasmic inclusions in respiratory
epithelium
Rickettsia rickettsii
Rocky Mountain Spotted Fever
Tick bite
Fever, severe headache, rash
starting at wrists/ankles → spreads
centrally, myalgia
Vasculitis with endothelial swelling, necrosis,
vascular leakage → petechial rash
Rickettsia prowazekii
Epidemic Typhus/Typhus Fever
Louse feces inoculation
(human body louse)
High fever, rash (starts on trunk →
extremities, spares palms/soles),
delirium
Endothelial necrosis, perivascular mononuclear
infiltrates, small hemorrhages
Orientia tsutsugamushi
Scrub Typhus
Mite (chigger) bite
Fever, eschar at bite site, rash,
lymphadenopathy
Necrotizing vasculitis of small vessels with
lymphocytic infiltrate
Feature
Candida
Cryptococcus
Pneumocystis
Aspergillus
Mucor / Rhizopus
Morphology
Budding yeast + pseudohyphae
Encapsulated yeast
Cysts (no hyphae)
Septate hyphae, 45°
branches
Non-septate, 90° branches
Main Host
Immunocompromised, diabetics
AIDS, immunocompromised
AIDS (CD4 <200)
Neutropenic, TB cavity
Diabetic ketoacidosis
Stain
PAS, GMS
India ink, mucicarmine
Silver stain
GMS
GMS
Key Lesion
White plaques, microabscess
Gelatinous meningoencephalitis
Frothy alveoli
Fungus ball / infarcts
Black necrosis of
sinuses/brain
PATHOLOGY REVIEWER
LONG EXAM 2
Fungus / Causative
Agent
INFECTIOUS DISEASES
Disease
Mode of Transmission / Predisposing
Factors
Signs & Symptoms
Histological & Gross Findings
Yeast Infections
Candida albicans
Candidiasis (superficial,
mucocutaneous, systemic)
Normal flora overgrowth (opportunistic);
spread by contact; risk ↑ with antibiotics,
diabetes, immunosuppression, catheters
- Oral thrush: white plaques on
tongue/mucosa, scrapable
- Vaginal candidiasis: pruritus, curdlike discharge
- Cutaneous: intertriginous rash,
paronychia
- Systemic: fever, sepsis in
immunocompromised
Cryptococcus
neoformans
Cryptococcosis
Inhalation of pigeon droppings / soil;
affects immunocompromised (esp.
AIDS)
Meningoencephalitis: headache,
fever, neck stiffness Pulmonary:
cough, dyspnea Disseminated: skin
papules (umbilicated)
Thick polysaccharide capsule (clear halo on India ink
stain, red on mucicarmine stain); soap-bubble lesions in
brain (gelatinous pseudocysts in gray matter)
Pneumocystis jirovecii
(formerly P. carinii)
Pneumocystis pneumonia
(PCP)
Airborne; reactivation in
immunocompromised (esp. HIV/AIDS,
CD4 <200)
Nonproductive cough, dyspnea, fever,
hypoxia; diffuse interstitial infiltrates on
chest X-ray
Foamy, eosinophilic alveolar exudate; cysts on silver
stain (cup- or crushed-disk-shaped); interstitial
pneumonitis with mononuclear infiltrates
Budding yeast with pseudohyphae; Germ tube
positive; in tissue: yeast + hyphae with neutrophilic
infiltrate; microabscesses in involved organs
Mold Infections (Filamentous Fungi)
Aspergillus fumigatus,
A. flavus, etc.
Aspergillosis (allergic,
colonizing, invasive)
Inhalation of spores; opportunistic in
immunocompromised, neutropenic, or
those with lung cavities (e.g., TB)
Mucor, Rhizopus,
Absidia spp.
Zygomycosis /
Mucormycosis
Inhalation of spores; opportunistic esp. in
diabetic ketoacidosis, leukemia,
immunosuppression
Blastomyces
dermatitidis
Blastomycosis
- Allergic bronchopulmonary
aspergillosis: asthma-like
- Aspergilloma (fungus ball): in lung
cavities → hemoptysis
- Invasive: pneumonia, vascular
invasion → infarcts
Rhinocerebral mucormycosis: nasal
congestion, necrotic black eschar on
palate or nasal mucosa, facial pain,
orbital involvement, brain invasion
Dimorphic Fungi (Mold in Cold, Yeast in Heat)
Inhalation of spores from soil/decaying
wood, especially in Mississippi & Ohio
River valleys, Great Lakes region
Pulmonary: pneumonia-like illness,
cough, fever
Cutaneous: ulcerated or verrucous
skin lesions
Disseminated: bone and GU
involvement (osteomyelitis,
prostatitis)
Septate hyphae, acute-angle (45°) branching;
angioinvasion → hemorrhagic infarcts; aspergilloma
appears as brown mass in lung cavity on gross exam
Non-septate broad hyphae with right-angle (90°)
branching; angioinvasion with tissue necrosis;
grossly black necrotic lesions (especially in
sinuses/orbit/brain)
Broad-based budding yeast with thick double
refractile wall; suppurative granulomas with mixed
neutrophilic & mononuclear infiltrates
PATHOLOGY REVIEWER
LONG EXAM 2
Parasite / Causative Agent
INFECTIOUS DISEASES
Disease / Type
Transmission & Infectious
Stage
Signs & Symptoms
Histologic & Gross Findings
Protozoal Infections
Plasmodium spp.
(falciparum, vivax, ovale,
malariae, knowlesi)
Babesia microti
Malaria
Infectious stage: Sporozoites via
female Anopheles mosquito bite
Cyclic fever with chills, anemia,
splenomegaly;
P. falciparum → cerebral malaria,
blackwater fever;
P. vivax/ovale → relapsing due to
hypnozoites
Hemozoin pigment in
macrophages, RBCs with
trophozoites (ring forms);
splenomegaly, congestion,
brown-black spleen/liver
Babesiosis
Infectious stage: Sporozoites via
Ixodes tick bite (same vector as
Lyme disease)
Fever, hemolytic anemia, fatigue;
may resemble malaria but no
periodic fever; worse in
splenectomized/immunocompromised
Maltese cross tetrads inside
RBCs (on Giemsa stain);
hemolysis without pigment
deposition
- Cutaneous: ulcerating skin lesions
("oriental sore")
- Mucocutaneous: destruction of
nasal/oral mucosa
- Visceral (Kala-azar): fever,
hepatosplenomegaly, pancytopenia,
dark skin
Amastigotes (LeishmanDonovan bodies) within
macrophages (oval organisms with
nucleus + kinetoplast);
granulomatous inflammation in
viscera
Leishmania donovani, L.
tropica, L. braziliensis
Leishmaniasis
(Visceral, Cutaneous,
Mucocutaneous forms)
Infectious stage: Promastigote
from sandfly bite
Trypanosoma brucei
gambiense / rhodesiense
African
Trypanosomiasis
(Sleeping sickness)
Infectious stage: Trypomastigote
from tsetse fly bite
Intermittent fever, lymphadenopathy,
Winterbottom’s sign (posterior
cervical nodes), somnolence, coma
(CNS invasion)
Trypomastigotes in blood/CSF,
perivascular inflammation in brain,
microglial nodules
Trypanosoma cruzi
American
Trypanosomiasis
(Chagas disease)
Infectious stage: Trypomastigote
from Reduviid (“kissing”) bug
feces
Acute: fever, lymphadenopathy,
chagoma (bite site swelling),
Romana’s sign (periorbital edema)
Chronic: cardiomyopathy,
megacolon, megaesophagus
Amastigotes in cardiac muscle
fibers, myofiber necrosis with
lymphohistiocytic infiltrate; fibrosis
in chronic phase
PATHOLOGY REVIEWER
LONG EXAM 2
Parasite / Causative
Agent
Disease / Type
INFECTIOUS DISEASES
Transmission & Infectious Stage
Signs & Symptoms
Histologic & Gross Findings
Metazoan/Helminthic Infections
Pruritic rash at entry site (“ground itch”), cough, GI
Infectious stage: Filariform larvae
pain, diarrhea; in immunocompromised →
penetrating skin (soil)
hyperinfection syndrome with sepsis
Larvae in intestinal mucosa, eosinophilic infiltrate;
mucosal ulceration; may see larvae in lungs/liver
(dissemination)
Strongyloides
stercoralis
Strongyloidiasis
Taenia solium / Taenia
saginata
Tapeworm infection
(Cestodes)
Neurocysticercosis (T.
solium only)
Infectious stage: Cysticercus larva
in undercooked pork (T. solium) or
beef (T. saginata); Egg ingestion →
cysticercosis
Usually mild GI symptoms; neurocysticercosis
→ seizures, hydrocephalus
Larval cysts in brain/muscle; scolex visible in cyst;
intestinal adult worms show proglottids in stool
Trichinella spiralis
Trichinosis
(Trichinellosis)
Infectious stage: Encysted larvae in
undercooked pork or wild game
Myalgia, fever, periorbital edema, eosinophilia;
may cause myocarditis, encephalitis
Encysted spiral larvae in skeletal muscle fibers;
intense eosinophilic and lymphocytic infiltrate
Schistosoma
haematobium, S.
mansoni, S. japonicum
Schistosomiasis
(Bilharziasis)
Infectious stage: Cercariae
penetrate skin from contaminated
freshwater (snails = intermediate
host)
- S. haematobium: hematuria, bladder fibrosis,
SCC risk - S. mansoni / japonicum: portal
hypertension, hepatosplenomegaly
Eggs with spines in tissues (terminal/lateral),
granulomatous inflammation, periportal fibrosis
(pipestem fibrosis)
Wuchereria bancrofti /
Brugia malayi
Lymphatic Filariasis
(Elephantiasis)
Infectious stage: Filariform larvae
via mosquito bite
Lymphedema → massive swelling of
limbs/scrotum; fever, lymphangitis
Adult worms in lymphatics, lymphatic obstruction,
fibrosis, chronic inflammation
Onchocerca volvulus
Onchocerciasis (River
Blindness)
Infectious stage: Filariform larvae
from blackfly bite (Simulium)
Pruritic papules, dermatitis, subcutaneous
nodules, progressive visual loss / blindness
Microfilariae in skin and eye, granulomatous
inflammation in cornea and dermis; fibrosis →
sclerosing keratitis
Group
Key Infectious Stage
Vector / Transmission
Hallmark Pathology
Organs
Plasmodium
Sporozoite
Anopheles mosquito
RBC lysis, pigment-laden macrophages
Blood, spleen, liver
Babesia
Sporozoite
Ixodes tick
RBC infection without pigment
Blood
Leishmania
Promastigote
Sandfly
Amastigotes in macrophages
Skin, liver, spleen
Trypanosoma cruzi
Trypomastigote
Reduviid bug
Myocardial amastigotes
Heart, GI
Strongyloides
Filariform larvae
Skin penetration
Larval invasion, eosinophilia
Intestine, lung
Taenia
Cysticercus
Undercooked meat
Cysts in brain/muscle
CNS, muscle
Trichinella
Encysted larvae
Undercooked meat
Larvae in muscle fibers
Muscle
Schistosoma
Cercaria
Skin penetration
Egg granulomas, fibrosis
Liver, bladder
Filaria
Filariform larvae
Mosquito
Lymphatic obstruction
Lymphatics
Onchocerca
Filariform larvae
Blackfly
Dermatitis, corneal fibrosis
Skin, eyes