Systemic dissemination by a newly recognized intestinal microsporidia species in AIDS

Objective: Primarily to determine whether an intestinal microsporidian recently identified in AIDS patients disseminates from the bowel to infect other organs. Design: Disseminated microsporidiosis has been reported in immunocompromised humans, but never due to Enterocytozoon bieneusi, the most common species in AIDS patients and one that evidently infects only enterocytes. In animals, dissemination follows ingestion of Encephalitozoon cuniculi spores, apparently via macrophages, and pathology occurs in, for example, kidneys and brain. A second, un-named Encephalitozoon-like intestinal microsporidia has been identified in five AIDS patients with chronic diarrhea; because it infects lamina propria macrophages, it was logical to investigate its dissemination. Methods: Light and transmission electron microscopy were used to study urine sediment from four out of five patients with biopsy-documented small intestinal infection due to the second intestinal microsporidian. The gall bladder from one patient and autopsy specimens from an E. bieneusi-infected patient were similarly studied. Results: Systemic dissemination was documented by detecting abundant spores, both free and within renal tubular and transitional cells, in the urine of two patients. Many of the lamina propria macrophages in these two patients' intestinal biopsies contained microsporidia, while those of the two negative patients either contained only Mycobacterium avium complex or only occasional parasites. The gall bladder was co-infected with this microspordian and with cytomegalovirus. At autopsy, the patient with documented enteritis due to E. bieneusi 2 years before death had disseminated microsporidiosis, not of E. bieneusi, but apparently of the second intestinal species. The microsporidian had caused severe tubulointerstitial nephritis. Parasites were also observed in non-parenchymal cells of the liver and bronchial epithelium. Conclusion: A newly described Encephalitozoon-like intestinal microsporidian, which causes chronic diarrhea in AIDS patients, can disseminate and cause renal pathology.