Atypical presentations of thrombotic thrombocytopenic purpura: a diagnostic role for ADAMTS13.

Thrombotic thrombocytopenic purpura (TTP) is an acute, life threatening disease. Only a minority of patients expresses the complete clinical presentation and unusual manifestations can occur. Demonstration of low activity levels of ADAMTS13 (<5 %) is highly specific for the diagnosis of TTP. This study reports a series of five cases of TTP presenting with a thrombotic event and no hematological findings. Detailed chart reviews on these patients were conducted. We identified two patients whose first attack of TTP presented as a thrombotic episode without microangiopathic hemolytic anemia and thrombocytopenia, only to be diagnosed as TTP days later, after the appearance of hematological signs. We also describe three cases of classical TTP relapsing atypically as cerebrovascular accidents without hematological signs. Low levels of ADAMTS13 activity were detected and facilitated the diagnosis. The neurological manifestations disappeared concurrent with normalization of ADAMTS13 activity level after plasma exchange. This study underscores the importance of having a high clinical suspicion of TTP in cases of thrombosis even without hematological abnormalities in patients with previous attacks of TTP. In this clinical scenario, measurement of ADAMTS13 activity is important for diagnosis and early administration of treatment.