Cryptosporidiosis in Hyper IgM Syndrome

The patient was an 8-year-old boy known case of hyper IgM (HIGM) syndrome since the age of 2 years with vomiting, abdominal pain, and chronic diarrhea for two months. He underwent upper gastrointestinal endoscopy after unsuccessful empirical therapy. Histologic examination of duodenum revealed variable villus atrophy with round basophilic microorganisms on the surface measuring 2 to 5 micrometers in diameter (Figure 1). Laboratory tests revealed elevated IgM (506 mg/dL, normal range = 31–208) and decreased IgG (302 mg/dL, normal range = 572–1474), IgA (2 mg/dL, normal range = 27–195), and IgE (