TTP is a differential diagnosis of other syndromes characterized by the presence of thrombocytopenia and microangiopathic hemolytic anemia such as HUS, disseminated intravascular coagulation (DIC), the "catastrophic" anti-phospholypid syndrome (APS), eclampsia, pre-eclampsia, HELLP syndrome and heparin induced thrombocytopenia (HIT) (31,32).

The main clinical and laboratory features useful to distinguish TTP from other thrombotic microangiopathies are summarized in Table 3.