Background: Plasma exchange (PE) therapy has dramatically improved theoutcome of thrombotic microangiopathies (TMA) in adults. However, resistance to PE, which indicates apoor prognosis, is observed in 1/3 of patients and remains not fully understood. We evaluated in thisstudy the survival and the long-term outcome of severe TMA treated by PE and identified the predictivefactors of resistance to PE and of mortality. Material/Methods: Records of adults with severe TMA treatedby PE were reviewed. Clinical and biological data, therapeutic delay to PE, plasma volume exchange perprocedure, and number of PE sessions were collected. Mortality was assessed at one month and at one-yearfollow-up. All data were analyzed and compared between survived/deceased and between responder/non-responderpatients. Results: Nineteen females and six males were included. Mean age (+/-SD) was 46.8+/-16.3 years,Glasgow coma score 11+/-3, and Sequential Organ Failure Assessment (SOFA) score 5.8+/-2.8. Nineteen patientspartially or fully responded to PE. Twenty patients were alive at one month and 19 at one year. The responseto PE was the single discriminating parameter between survivors and non-survivors. A longer delay ofPE and a neoplastic cause of TMA were significantly higher in the non-responders. Conclusions: SevereTMA treated by PE had a fair prognosis, with a survival rate at 76% after one year of follow-up. Unresponsivenessto PE was the only predictive factor of mortality; a neoplastic etiology of TMA and a longer therapeuticdelay of PE were predictive of resistance to PE.

Keywords: Plasma Exchange, Thrombosis - therapy, Vascular Diseases - therapy