Thienopyridine-Associated Thrombotic Thrombocytopenia Purpura: Updated Antibody Results From the SERF-TTP Study.

The thienopyridines, ticlopidine and clopidogrel, have been associated with thrombotic thrombocytopenia purpura (TTP). However, few studies have reported information on antibodies to ADAMTS13 among patients with thienopyridine-associated TTP. We previously reported on two mechanistic pathways of thienopyridine-associated TTP with some overlapping features. Evaluation of ADAMTS13 autoantibodies was undertaken to improve understanding of these syndromes.

Clinical and laboratory findings were evaluated for 30 ticlopidine-, 10 clopidogrel-associated TTP cases, and 54 cases of idiopathic TTP.

Among patients with thienopyridine-induced TTP, those with a history of ticlopidine versus clopidogrel use were more likely to present with severe thrombocytopenia (platelet < 20,000) (90% versus 13%), severe ADAMTS13-deficiency (80% versus 0%), and neutralizing antibodies to ADAMTS13 (100% versus 0%), and were less likely to have less than a two week history of thienopyridine exposure (0% versus 50%) (p<0.05 for each comparison). They were also more likely to survive following therapeutic plasma exchange (TPE) (85% versus 50%). 2 patients exposed to clopidogrel later relapsed and had similar characteristics to idiopathic TTP patients with non-deficient ADAMTS13 activity.

Ticlopidine causes TTP by a pathway involving a neutralizing autoantibody to ADAMTS13 while clopidogrel causes TTP by an ADAMTS13-independent pathway. Although ADAMTS13 autoantibodies are present in both idiopathic and ticlopidine-associated TTP, spontaneous relapses are not seen in ticlopidine-associaated TTP, suggesting that drug-dependent antibodies are present. Clopidogrel associated TTP is distinct from idiopathic TTP in that ADAMTS13 autoantibodies are absent and response to TPE is poor.

No relevant conflicts of interest to declare.