The clinical syndrome of fever, neurologic abnormalities, renal impairment with 
laboratory findings of thrombocytopenic and microangiopathic hemolytic anemia is 
seen in thrombotic thrombocytopenic purpura (TTP) and a variety of disorders 
associated with thrombotic microangiopathy (TMA). With improved understanding of 
the pathogenesis of the perturbed metabolic pathway of von Willebrand factor in 
TTP, the classic Moschcowitz syndrome, now more accurately referred to as 
idiopathic TTP, can be distinguished from other TMAs. The distinguishing 
features are useful not only in providing an accurate diagnosis but also help to 
determine the best therapeutic strategy.