Thrombotic thrombocytopenic purpura (TTP) is a severe microvascular occlusive microangiopathy characterized by thrombocytopenia, Coombs-negative hemolytic anemia and ischemic symptoms localized mainly but not exclusively in central nervous system and resulting from diffuse platelet thrombi in the microcirculation (1).

TTP, though uncommon, is a life threatening disorder with acute onset and often a fulminant-fatal course: the annual incidence is 3.7 cases per 10 individuals (2), possibly slightly increasing during recent years. Even though both sexes may be affected, the disease is definitely more frequent in women (two third of the cases). Without treatment the mortality rate is greater than 90%, while becomes 10-20% with plasma infusion or plasma exchange treatment.

In most cases TTP occurs as a single, sporadic acute episode; however 20 to 50% of patients who survive an acute episode, relapse (more often but not always within 6 months), developing a chronic recurrent form of the disease (3,7).