Background: Cystoisosporiasis is an opportunistic infection seen more commonly in patients with acquired immunodeficiency syndrome. Although uncommon, Cystoisospora infection can occur in immunocompetent individuals but tend to be benign and self-limiting. Chronic infection however, has been described but diagnosis can often be challenging and requires a high clinical index of suspicion. Case presentation: We present a case of delayed diagnosis of Cystoisospora belli (C. belli) in an immunocompetent 28-year-old refugee from Myanmar. She had a history of chronic diarrhea where exhaustive investigations over many years failed to reveal a diagnosis. Cystoisospora belli cysts were finally detected in stool 4 years after investigation commenced, and PCR testing on stored colon biopsies amplified a molecular product with 99 % sequence homology to C. belli. The patient improved promptly with trimethoprim-sulfamethoxazole treatment. Conclusion: In the appropriate clinical context we suggest molecular testing for C. belli or an empirical therapeutic trial. © 2016 Woon et al.

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genetics duodenitis endoscopic biopsy parasitology Isospora belli Eosinophilia refugee cytology Immunocompromised Host vomiting physiology abdominal pain parasite identification complication clinical feature human Refugees immunocompromised patient feces analysis statistics and numerical data chronic diarrhea hypokalemia Acquired Immunodeficiency Syndrome nausea nonhuman chronic disease procedures Humans case report female Albendazole evaluation study Myanmar polymerase chain reaction immunology isolation and purification Article cotrimoxazole Trimethoprim, Sulfamethoxazole Drug Combination adult Feces microscopy acquired immune deficiency syndrome metronidazole isosporiasis coccidiosis Sarcocystidae