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The Role of Microsporidia in the Pathogenesis of HIV-Related Chronic Diarrhea

Linda Rabeneck, MD, MPH; Ferenc Gyorkey, MD; Robert M. Genta, MD; Phyllis Gyorkey, MS; Lorraine W. Foote, RN; and Jan M. H. Risser, MS
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From the Veterans Affairs Medical Center, Baylor College of Medicine, and the Veterans Affairs Electron Microscopy Program and Veterans Affairs Research Center for AIDS and HIV Infection, Houston, Texas. Requests for Reprints: Linda Rabeneck, MD, Veterans Affairs Medical Center (111D), 2002 Holcombe Boulevard, Houston, TX 77030. Grant Support: In part by a Baylor College of Medicine Biomedical Research Support Grant (USPHS grant RR-05425); the Houston Veterans Affairs Research Center for AIDS and HIV Infection, the Houston Veterans Affairs Electron Microscopy Program, a Veterans Affairs Center of Excellence; and an American College of Gastroenterology Clinical Research Award.

Copyright 2004 by the American College of Physicians

Ann Intern Med. 1993;119(9):895-899. doi:10.7326/0003-4819-119-9-199311010-00005
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Objective: To determine whether infection with Microsporidia leads to diarrhea in patients with human immunodeficiency virus (HIV) infection.

Design: Case-control study.

Setting: Primary care outpatient HIV clinic at a Veterans Affairs medical center.

Patients: One hundred six HIV-infected men, 55 with and 51 without chronic diarrhea.

Measurements: Each patient underwent upper endoscopy and flexible sigmoidoscopy to obtain duodenal, rectal, and sigmoid colonic biopsy specimens. At the time of endoscopy, a fresh stool was obtained for culture, ova and parasite assessment, and Cryptosporidium examination. Biopsy tissue was examined using electron microscopy to detect Microsporidia.

Results: The microsporidian parasite Enterocytozoon bieneusi was detected in the duodenal biopsy specimens of 31 of 106 men (29%); 24 of 106 men (23%) had other enteric pathogens. No significant difference was observed in the occurrence of microsporidiosis in patients with (18 of 55 [33%]) and without (13 of 51 [25%]) chronic diarrhea (odds ratio, 1.42; 95% CI, 0.61 to 3.31). A similar nonsignificant difference was observed after controlling for CD4 count and other enteric pathogens (odds ratio, 1.66; 95% CI, 0.68 to 4.06). Among patients with microsporidiosis, no difference was observed in the intensity of infection (defined by the presence of few, moderate, or abundant organisms) among cases and controls (P > 0.2).

Conclusions: This is the first report to document the presence of E. bieneusi in HIV-positive patients without gastrointestinal symptoms. No significant difference was observed in the occurrence of E. bieneusi infection in HIV-infected patients with or without chronic diarrhea. Thus, the association between microsporidiosis and diarrhea, if one exists, may not be as strong as is currently believed.


Grahic Jump Location
Figure 1.
Electron graph of early proliferative plasmodia (thin arrows) and later sporogonial plasmodium (thick arrow) of Enterocytozoon bieneusi in a duodenal biopsy specimen.

N = enterocyte nucleus; a = electron dense disc; b = one of several nuclei contained in the plane of section. (Original magnification, 10 000.).

Grahic Jump Location
Grahic Jump Location
Figure 2.
Electron graph of mature spores (arrows) of Enterocytozoon bieneusi in a duodenal biopsy specimen.

(Original magnification, 10 000.).

Grahic Jump Location




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