Frequently relapsing thrombotic thrombocytopenic purpura treated with cytotoxic immunosuppressive therapy.

BACKGROUND AND OBJECTIVES Treatment of thrombotic thrombocytopenic purpura (TTP) with plasma exchange has reduced mortality rates from 90% in untreated cases to less than 20%. Despite plasma exchange, relapses may occur in as many as 40% of cases. Multiple relapses occur in a minority but pose a significant therapeutic challenge. Recent evidence supports the presence of an autoantibody which inhibits proteolysis of von Willebrand factor (vWF) in active TTP, allowing large multimers of vWF to form and promote platelet aggregation. Additional evidence suggests autoantibodies activate capillary endothelium and promote platelet aggregation in the microcirculation. Immunosuppression, thus, has a biologically plausible role in TTP. We describe three consecutive cases of relapsing TTP treated with cytotoxic therapy to highlight the potential role of immunosuppression. DESIGN AND METHODS Cytotoxic immunosuppressive therapy with either cyclophosphamide or azathioprine was used in three consecutive patients with frequently relapsing TTP. RESULTS All three patients have maintained remissions of 8 to 10 months without recurrence. INTERPRETATION AND CONCLUSIONS Cytotoxic immunosuppressive therapy may have a role in inducing long-term remissions in recurrent TTP.