A rare leucine 40/arginine40 polymorphism on platelet glycoprotein IIIa is linked to the human platelet antigen 1b.

A rare polymorphism on glycoprotein (GP) IIIa is reported. Sequencing of a 482-base-pair (bp) PCR product of the genomic DNA of GPIIIa revealed a single-base exchange of a G<==>T polymorphism at base 12,569 that created an additional restriction site for MspI. This single-point mutation (frequency in Caucasians 0.00386) is on the HPA-1b gene (HPA-1bvar) and codominantly inherited. The exchange of a G for a T results in a leucine-to-arginine substitution at amino acid 40 from the NH2 terminus. The binding of anti-HPA-1a and -1b antibodies to HPA-1bvar platelets is not influenced.