Diagnostic Challenges of Cyclosporiasis in Chronic Diarrhea: A Case Study

Cyclosporiasis, caused by <i>Cyclospora cayetanensis</i>, is a rare opportunistic infection, particularly in immunosuppressed patients with inflammatory bowel disease (IBD). Its clinical presentation may mimic IBD, with chronic diarrhea and anemia resistant to standard therapy. We report the case of a 24-year-old woman with ulcerative colitis (UC) and a history of liver transplantation, treated with vedolizumab and immunosuppressants. Despite endoscopic remission, she experienced persistent abdominal pain, diarrhea, and iron deficiency anemia. Escalation of biologic therapy was ineffective. After exclusion of bacterial and viral causes, stool testing identified <i>Cyclospora cayetanensis</i>. Treatment with nitazoxanide led to rapid clinical and laboratory improvement. Biologic therapy was temporarily discontinued and later resumed without recurrence of symptoms. This case shows that chronic diarrhea in IBD patients may not always result from the underlying disease. Immunosuppression increases the risk of opportunistic infections. Early diagnosis and specific treatment can improve outcomes and allow safe continuation of IBD therapy.