ROSH Gastrointestinal Practice Exam

Which infectious etiology is the most common cause of diarrhea in patients with AIDS?

1. Clostridium difficile

2. Cytomegalovirus

3. Cryptosporidium

4. Mycobacterium avium complex

The correct answer is: Cryptosporidium

Cryptosporidium is indeed the most common infectious cause of diarrhea in patients with AIDS. This protozoan parasite is a significant opportunistic infection particularly in individuals with a CD4 count below 200 cells/mm³. In these patients, Cryptosporidium often leads to severe, watery diarrhea, which can result in significant fluid loss and dehydration. The reason Cryptosporidium is so prevalent in this population is related to the compromised immune system of patients with AIDS, leaving them vulnerable to infections that a healthy immune system would typically fend off. In immunocompromised individuals, the Giardia or E. coli pathogens often seen in non-HIV related cases tend to be less common. While Clostridium difficile is an important cause of diarrhea, especially in the context of antibiotic use, it is not as closely associated with AIDS as Cryptosporidium. Similarly, Cytomegalovirus can cause gastrointestinal symptoms, but it is less frequent as a direct cause of diarrhea compared to Cryptosporidium. Mycobacterium avium complex may also lead to gastrointestinal manifestations, but it primarily presents with systemic symptoms rather than the isolated diarrhea seen with Cryptosporidium. This highlights the importance of understanding the specific infectious profiles associated with immunocompromised states