This serious disorder of young adults is characterized by fever, hemolytic anemia, hemorrhagic signs, various neurologic abnormalities and renal dysfunction. Laboratory findings include a negative Coombs' test for hemolytic anemia, severe thrombocytopenia, and fragmented erythrocytes on the peripheral blood smear. Without treatment, mortality may exceed 80 percent. Early diagnosis and prompt therapy with high-dose corticosteroids and antiplatelet agents, as well as exchange plasmapheresis when indicated, bring about remission in 60 to 80 percent of patients.