Investigation of a platelet factor 4 polymorphism on the immune response in patients with heparin-induced thrombocytopenia

A small fraction of patients who receive heparin develop heparin-induced th rombocytopenia (HIT) and, of these patients, a still smaller proportion dev elop associated thrombotic complications, Heparin-induced thrombocytopenia is caused by the formation of antibodies that bind to specific complexes of platelet factor 4 (PF4) and heparin. However, it remains uncertain why cer tain patients form these antibodies and develop HIT or why certain patients have thrombotic events. In this report we describe studies on individuals with and without HIT to determined if a potential PF4 polymorphism could ex plain differences in susceptibility to HIT. In the 10 control individuals a nd the 10 patients we studied, we did not find a difference in the PF4 sequ ences. Genetic difference in the PF4 antigenic target does not explain the occurrence of HIT in susceptible patients.