Phillip D. Smith1, C. Mel Wilcox1, and Edward N. Janoff2 1University of Alabama at Birmingham, Birmingham, AL, USA 2University of Colorado Health Sciences Center, Denver, Aurora, CO, and Veterans Affairs Medical Center, Denver, CO, USA The acquired immunodeficiency syndrome (AIDS) and other cellular and humoral immunodeficiency states are associated with an array of gastrointestinal complications. The complications associated with AIDS are caused predominantly by infection. Parasitic (mainly protozoal), viral, bacterial, and fungal pathogens cause a spectrum of mucosal disease, depending on the location and severity of infection and the degree of immunosuppression induced by human immunodeficiency virus‐1 (HIV‐1), the causative agent of AIDS. These pathogens are considered opportunistic in immunosuppressed persons because they occur more frequently, cause more severe disease, and are associated with more prolonged or recurrent infection. Opportunistic pathogens in patients with advanced HIV‐1 disease more frequently develop resistance to antimicrobial agents than do the same pathogens in immunocompetent persons. Gastrointestinal complications are also associated with allogeneic hematopoietic stem cell and solid organ transplantation. Graft‐versus‐host disease, which must be differentiated from infectious processes, is the most common gastrointestinal complication of hematopoietic stem cell transplantation. Opportunistic enteric infections, particularly cytomegalovirus, also commonly complicate solid organ transplantation. This chapter focuses on endoscopic and histological features of gastrointestinal infections associated with AIDS, hepatic complications of AIDS, and intestinal involvement in graft‐versus‐host disease (Figures 67.1–67.14). Figure 67.1 Cryptosporidium parvum is a parasitic protozoan that causes prolonged, often profuse, watery diarrhea in immunosuppressed persons with HIV‐1 infection, particularly in the developing world. (a) Acid‐fast stained stool specimen shows round Cryptosporidium oocysts 4–6 μm in diameter (modified Kinyoun stain; magnification ×630). (b) Light microscopic image shows Cryptosporidium protozoa lining the luminal surface of the epithelium in an intestinal biopsy specimen from a patient with chronic diarrhea (hematoxylin and eosin; magnification ×400). (c) Electron micrograph of an intestinal biopsy section shows a Cryptosporidium trophozoite that has displaced the microvilli to attach to the apical surface of an epithelial cell (magnification ×12 500). Source: Janoff EN. Cryptosporidium. The Immunocompromised Host 1988;5:1. Figure 67.2 Microsporidia protozoa in the small intestine of persons with HIV‐1 infection is associated with a chronic diarrheal illness that clinically resembles cryptosporidiosis. (a) The intensity of infection is greatest in the jejunum, where densely stained elliptical spores are detected in the epithelial cell cytoplasm by light microscopic examination (semithin plastic section, methylene blue‐azure II, basic fuchsin stain; original magnification ×630). (b) Electron micrograph shows a necrotic intestinal enterocyte in the final stage of being sloughed into the lumen; the enterocyte contains six microsporidian spores (magnification ×10 000). Source: Reproduced with permission of Dr Jan M. Orenstein. Figure 67.3 The coccidian protozoan Isospora belli causes a mild, self‐limited diarrheal illness among immunocompetent persons but prolonged diarrhea among immunosuppressed persons. Infection with I. belli is diagnosed by identification of large (20–30 μm by 10–19 μm), oval, acid‐fast oocysts that contain two sporoblasts in a fresh stool specimen (modified Kinyoun stain; magnification ×630).
CHAPTER 67
Complications of HIV/AIDS and other secondary immunodeficiency states
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