Thrombotic Thrombocytopenic Purpura

A 40-year-old obese black woman has had weakness and epigastric pain for several weeks and diarrhea and vomiting for four days. She does not appear acutely ill; the physical examination is normal except for abdominal tenderness. Her hematocrit is 25 percent. The platelet count is 10,000 per cubic millimeter. The peripheral-blood smear shows occasional fragmented and polychromatophilic red cells. The serum creatinine level is 1.1 mg per deciliter (97.2 μmol per liter), bilirubin 2.5 mg per deciliter (42.8 μmol per liter), and lactate dehydrogenase 722 U per liter (normal,