Thrombotic thrombocytopenic purpura–hemolytic uremic syndrome (TTP–HUS) is an uncommon but serious illness that can cause death. In TTP–HUS, several organs (kidney, brain) get clogged with fragments of red blood cells and platelets. Red cells are broken down faster than they can be replaced (hemolytic anemia). Blood-clotting cells called platelets are reduced (thrombocytopenia) because they get stuck in the areas containing red blood cell fragments. Abnormal clotting or thrombosis results in many parts of the body. Symptoms include confusion, kidney failure, and increased bruising (purpura). Immediate treatment with exchange of plasma (blood fluid without blood cells) prevents death in most patients. This disorder may be caused by an abnormal immune reaction (to a drug or other agent), in which the body produces antibodies that attack many cell types. Quinine, a drug used to treat leg cramps and available in nutrition stores, is the most common cause of drug-related TTP–HUS. The course and outcomes of quinine-associated TTP–HUS are not well known.