Varicella-associated thrombocytopenia: Autoantibodies against platelet surface glycoprotein V

Varicella tester infection in children can be complicated by acute idiopathic thrombocytopenic purpura (ITP). To determine the etiologic mechanism of this thrombocytopenia, we studied three children with clinically diagnosed varicella infection. Immunoblot analysis of these patients' anti-platelet antibodies identified a unique band at 85 kD. Characterization of this protein revealed that it was platelet surface glycoprotein V (GPV) because it was not affected by a disulfide bond reduction but was cleaved by thrombin. Bernard-Soulier syndrome (BSS) platelets deficient in GPIb-IX and GPV did not react with the sera from our varicella-infected study patients. There was no apparent cross-reactivity between anti-varicella antibody and patients' anti-GPV Ig. We report here the first cases of GPV as the target antigen in autoimmune thrombocytopenia.