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

<i>Cystoisospora belli</i> (<i>C. belli</i>) 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 <i>C. belli</i>, 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 <i>C. belli</i>. The patient received several courses of TMP-SMX with only partial improvement and requires ongoing secondary prophylaxis.