The remission rate with plasma exchange (PE) in thrombotic thrombocytopenic purpura (TTP) exceeds the 80%, but the disease relapses in up to 20–30% of the cases. Clinical characteristics and response to treatment of relapsed TTP is not well defined. The objective of the present study was to analyze the presenting clinical and biological features of relapsed TTP as compared with de novo TTP in a series of 102 TTP episodes (70 de novo and 32 relapses) followed prospectively and treated by daily PE and corticosteroids according to a homogeneous protocol. In comparison with de novo TTP, relapsed TTP episodes showed a higher Hb level (122 g/L versus 91 g/L, p<0.001) and lower serum LDH (2.2 versus 4.5 fold above the upper limit of normality, p<0.001). Neurological symptoms and fever were less frequent in patients with relapsed TTP than in patients with de novo TTP. There were no statistically significant differences in the percentage of patients with a severe deficit of ADAMTS13 activity (72% in de novo TTP versus 81% in relapsed TTP, p not significant) or the presence of inhibitory autoantibodies (87% versus 81%, p not significant). Patients with relapsed TTP needed fewer PE sessions (5 versus 10, p= 0.02) and a smaller volume of plasma (221 ml/kg versus 468 ml/kg, p=0.004) to achieve remission than those with de novo TTP. There were no significant differences in the rate of recrudescence under treatment, the need for complementary treatments (e.g. rituximab or splenectomy) or the frequency of refractoriness to PE therapy. In conclusion, relapsed TTP presents with a milder clinical and biological profile and responds easier to PE than de novo TTP.

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