Thrombotic Thrombocytopenic Purpura

A rare disorder of the blood coagulation system that is characterized by the formation of microscopic blood clots in small blood vessels throughout the body. Most cases of the disorder have no known cause, but some cases may be caused by a lack of the ADAMTS13 gene at birth that gives instructions for making the enzyme that is involved in clotting. The condition also may be related to cancer, chemotherapy, HIV infection, hormone replacement therapy and estrogens, and a number of commonly used medications (including ticlopidine, clopidogrel, and cyclosporine A). Symptoms include fever, weakness, fatigue, pallor, shortness of breath, bleeding into the skin, headache, confusion, changes in consciousness and jaundice.