Entamoeba Histolytica
Laura W. Lamps, MD
Key Facts
Etiology/Pathogenesis
Affects approximately 10% of world population
Clinical Issues
Nondysenteric infection: Milder symptoms
Dysenteric or invasive infection: Sudden, severe diarrhea, abdominal cramps
Macroscopic Features
Cecum most often affected
Ulcers most common lesion
Microscopic Pathology
Organisms have foamy cytoplasm; round, eccentric nucleus; ingested red blood cells
Closely resemble macrophages
Abundant, amorphous, eosinophilic debris may exceed amount of inflammation
Ulcers extend into submucosa (flask-shaped ulcer)
 Hematoxylin & eosin shows a characteristic flask-shaped ulcer extending into the submucosa. |
 Hematoxylin & eosin shows amoebae with foamy cytoplasm, round eccentric nuclei with open chromatin  , and ingested erythrocytes  . |
TERMINOLOGY
Synonyms
Amebiasis
Definitions
Infection by motile protozoan Entamoeba histolytica
ETIOLOGY/PATHOGENESIS
Distribution
Affects approximately 10% of world population
Primarily in tropical and subtropical regions
In USA, most often seen in immigrants, travelers, male homosexuals, institutionalized persons
