Colitis and Intestinal Granulomas in Acquired Immunodeficiency Syndrome

Granulomas consist of focal collections of immune cells that forms as a result of chronic inflammation. They can be formed in different organs and are considered the hallmark for several inflammatory and infectious diseases. The presence of granulomas in the mucosal biopsies of the gastrointestinal (GI) tract of immunocompetent patients, along with histological features of chronicity, confirms the diagnosis of Crohn's disease (CD) in the majority of cases. However, owing to their immunocompromised state, new-onset inflammatory bowel disease (IBD) is rare in patients with Acquired Immune Deficiency Syndrome (AIDS). In these patients, diarrhea is often due to the presence of an opportunistic infection, including bacteria (Salmonella, Mycobacterium avium complex (MAC)), protozoa (Cryptosporidia, Giardia), viruses (Cytomegalovirus, Herpes simplex virus) or fungi (Histoplasma). Infection by MAC is prevalent in patients with AIDS, but isolated involvement of GI tract by this organism is rare. Positive Acid-Fast Bacillus (AFB) stain and culture on mucosal biopsy usually establish the diagnosis. We report an unusual case of isolated MAC colitis that was originally misdiagnosed as CD. The AFB stain and culture were negative, indicating the importance of having a high suspicion for infectious etiologies when clinically indicated.