Which of the following is a major category of chronic diarrhea differential?

• A. Infectious disease
• B. Parasitism
• C. Neoplasia
• D. Non-GI disease

Answer: (A)

When evaluating chronic diarrhea, clinicians organize potential causes into broad categories to guide the work-up. The infectious disease category is a major one because a large share of chronic GI signs arise from persistent or occult infections—bacteria, viruses, fungi, or protozoa—that can drive ongoing inflammation and malabsorption. Identifying an infectious etiology is often actionable, with targeted tests (such as fecal PCR panels, cultures, or parasite testing) leading to specific therapies or eradication. While parasitism, neoplasia, and non-GI disease are also important parts of the differential, infectious disease stands out as a central, broad category that frequently shapes initial diagnostic and treatment decisions.