Ticlopidine-associated thrombotic thrombocytopenic purpura with an IgG-type inhibitor to von Willebrand factor-cleaving protease activity

A 41-year-old Japanese man complained of a left-sided visual disturbance. I maging by magnetic resonance angiography revealed a narrowing of the left i nternal cervical artery. Thus, ticlopidine (Tc) administration was started at a daily dose of 300 mg. However, 2 weeks later, severe thrombocytopenia, fever, nausea, and psychiatric symptoms developed; Tc was therefore discon tinued. Based on the diagnostic hallmark of 5 clinical signs, the patient's disease was diagnosed as thrombotic thrombocytopenic purpura (TTP). Daily plasmapheresis was performed for the first 4 days, and the patient's clinic al signs gradually improved. Von Willebrand factor-cleaving protease (vWF-C Pase) activity in his plasma was less than 3% of that of the control sample at diagnosis, but that value recovered steadily following plasmapheresis. In addition, immunaglobulin G purified from the patient plasma inhibited vW F-CPase activity in normal plasma with a specific activity of 0.8 Bethesda units/mg. No sign of TTP relapse has been noted following cessation of Tc. Thus, it was concluded that the patient developed TTP by producing an inhib itory autoantibody against vWF-CPase activity that was presumably triggered by Tc administration. (C) 2001 The Japanese Society of Hematology.