Genotyping provides a reliable tool for the determination of the platelet antigen system HPA-1 in Glanzmann's thrombasthenia.

Glanzmann's thrombasthenia (GT) is an inherited disorder of platelet function, characterized by quantitative or qualitative defects of the platelet glycoprotein (GP) IIb/IIIa complex. Patients with GT may require repeated transfusions and therefore alloimmunization against platelet antigens could become of particular interest. As GPIIIa contains the most important platelet alloantigen system, HPA-1, its diminished expression in GT patients may impede serological determination of the HPA-1 allotype. By immunofluorescence consistent results were obtained in only two out of seven patients. The monoclonal antibody-specific immobilization of platelet antigen test allowed typing of six patients. DNA analysis was feasible in all cases. All seven patients were identified to be homozygous HPA-1a. Thus, provided a normal HPA-1 DNA region, its analysis can serve as a reliable tool for HPA-1 typing in GT even if serological methods fail.