title: Encephalitozoon (Septata) intestinalis: cytologic, histologic, and electron microscopic features of a systemic intestinal pathogen.
abstract: Encephalitozoon (Septata) intestinalis affects AIDS patients with CD4 counts <100/microL, causing intestinal and disseminated disease. It must be distinguished from the more common intestinal microsporidian, Enterocytozoon bieneusi, and from other microsporidia of extraintestinal tissues, such as Encephalitozoon hellem and E cuniculi, because clinical manifestations and treatment differ. In this report, the authors describe the diagnostic features of E intestinalis and illustrate all stages of its life cycle as exemplified by a case studied in detail. Spores can be detected by light microscopy in feces, urine, or nasal secretions, but not identified to species. A presumptive tissue diagnosis of E intestinalis can be made if 20 to 50 organisms 1.2-2.5 microm in diameter are seen within vacuoles in enterocytes. The diagnosis is substantiated if organisms also are present in stromal cells. On electron microscopy, the septate parasitophorous vacuole is pathognomonic. E bieneusi occurs only in intestinal and biliary epithelial cells, and never within a vacuole. E hellem and E cuniculi, which are not intestinal pathogens, may cause systemic infection but develop in a nonseptate vacuole.
authors.affiliation: Department of Pathology, Yale University, New Haven, Connecticut, USA.
authors.forename: P
authors.initials: P
authors.lastname: Chu
authors.forename: A B
authors.initials: AB
authors.lastname: West
mesh_terms: D017088:AIDS-Related Opportunistic Infections / Q000469:parasitology / Q000473:pathology*; D000818:Animals; D004386:Duodenum / Q000469:parasitology / Q000473:pathology* / Q000648:ultrastructure; D016819:Encephalitozoon / Q000302:isolation & purification* / Q000648:ultrastructure; D016890:Encephalitozoonosis / Q000469:parasitology / Q000473:pathology*; D006801:Humans; D007411:Intestinal Diseases, Parasitic / Q000473:pathology*; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged