Matei Weiner, MD

A 32-year-old Hispanic woman with AIDS presented with a 1-month history of diarrhea; abdominal bloating and cramps; loss of appetite; and pronounced fatigue, malaise, and weight loss. She had no fever or chills and was not vomiting. Her CD4+ cell count was 12/µL. Results of a routine microscopic examination of stool for ova and parasites were negative; an acid-fast stain of stool demonstrated oocytes of Cyclospora cayetanensis measuring 8.8 mm in diameter (pictured, magnification ×1,000). This is about twice the size of the Cryptosporidium parvum oocyte, which typically is 4 to 5 mm.