Cholecystitis is one of the common surgical indications affecting human beings in many countries. A variety of infectious agents can be associated with acute or chronic acalculous cholecystitis, especially in HIV/AIDS patients. In this investigation, the authors aim to describe two cases of histologically and molecularly documented cystoisosporiasis (syn. isosporiasis) as the cause of chronic acalculous cholecystitis in two immunodeficient patients.

During microscopic examinations of more than 2500 diarrheic patients’ samples, 11 cases of cystoisosporiasis-related recurrent persistent/chronic diarrhea were detected. A review of the medical records of Cystoisospora belli (syn. Isospora belli)-positive patients showed that two of them, i.e. a patient with prolonged corticosteroid therapy and an AIDS patient, several months prior to fecal examinations had undergone cholecystectomy due to acalculous cholecystitis. The study was continued by a review of the histopathological investigation of the recuts prepared from the excised gallbladder tissue sections and stained with hematoxylin and eosin in order to detect a possible specific clinical correlation with cystoisosporiasis. Light microscopic examination revealed the presence of various developmental stages of a coccidial parasite, namely Cystoisospora belli, in both patients’ gallbladder tissue sections.

To the best of our knowledge, C. bellii-associated cholecystitis has not been previously reported in a patient with prolonged corticosteroid therapy.