The peripheral blood morphologic findings are those of microangiopathic hemolytic anemia, and consist of thrombocytopenia, and presence of schistocytes and spherocytes. Microangiopathic hemolysis is seen in any of a group of related conditions, all characterized by formation of thrombi in small vessels. Although uncommon, TTP is not as rare as once was thought. TTP is a clinical-pathologic diagnosis.
Few patients exhibit the full spectrum of abnormalities listed above.
While virtually all patients have thrombocytopenia and hemolysis, in recent years systemic symptoms are not universally found, possibly because treatment aborts the disease process before severe systemic manifestations can occur. Of systemic symptoms, neurologic findings are the most common. TTP may be associated with 3rd trimester pregnancy, autoimmune diseases, viral illnesses or be drug-related. Most cases, however, are idiopathic. The cause is not known, but may relate to a multifactorial process which, by an unknown mechanism, leads to formation of abnormally large von Willebrand factor multimers in the blood which then inappropriately activate platelet aggregation.