Recurrent Diarrhea Due to Cystoisospora belli in a Patient With HIV: A Case Report

Cystoisospora belli (C. belli) is an opportunistic protozoan that primarily affects immunocompromised individuals, including people living with human immunodeficiency virus (HIV). Although the widespread use of antiretroviral therapy (ART) and trimethoprim/sulfamethoxazole (TMP-SMX) prophylaxis has significantly reduced its global incidence, cases continue to be reported among individuals with inmune reconstitution. The pathogen remains a significant cause of chronic diarrhea, dehydration, and malabsorption syndrome in Latin America, contributing to increased morbidity and mortality. We present the case of a 27-year-old cisgender man living with HIV who experienced recurrent episodes of diarrhea due to C. belli, despite good adherence to ART and a CD4 count >200 cells/mm³. Initial parasitological stool examinations yielded negative results; however, a gastrointestinal multiplex polymerase chain reaction (PCR) panel subsequently identified C. belli. The patient received several courses of TMP-SMX with only partial improvement and requires ongoing secondary prophylaxis.