Increased risk of thrombosis in FcγRIIA 131RR patients with HIT due to defective control of platelet activation by plasma IgG2

Key Points Normal IgG and IgG2 differentially inhibit HIT antibody-dependent platelet activation according to the FcγRIIA H131R polymorphism. This variable effect of IgG and IgG2 probably explains the higher risk of thrombosis in patients homozygous for the FcγRIIA 131R allele.