Reported evidence suggests that HIV itself may be an indirect diarrheal pathogen because viral proteins have been found in the gut. HIV has been identified in histologic specimens from the GI tract tissue in up to 40% of patients.The virus is confined to lamina propria macrophages and enterochromaffin cells and has not found in epithelial cells. Intestinal HIV infection may also affect local humoral immunity and cause motility disturbances via effects on autonomic nerves.
An “idiopathic AIDS enteropathy” has been proposed to account for the diarrhea in HIV-infected patients who lack an identifiable pathogen. This syndrome may result from indirect effects of HIV on enteric homeostasis. Although the precise features of the syndrome are not agreed on, the term implies a chronic diarrheal illness with no identified etiology in patients with advanced HIV disease. Some advocate the inclusion of mucosal hypoproliferation as a defining feature. Enteric HIV infection may lead to mucosal atrophy, which in turn impairs small-bowel absorption, causing diarrhea and weight loss.