Heterogeneity in Glanzmann's Thrombasthenia

The activation-independent platelet adhesion to the fibrinogen-coated surface under static conditions was examined in patients with Glanzmann's thrombasthenia (type I: 5 cases; type II: 1 case). Among five type I patients, platelet adhesion in three patients was found to be less than 20% of that in normal controls, while two showed 66% and 89% adhesion, respectively. Platelet adhesion in one type II patient was normal. In all patients, platelet adhesion to fibronectin or collagen type I was much the same as that in normal controls.Binding of an anti-GPIIb/IIIa complex monoclonal antibody LJ-P9 to platelets, which completely inhibits platelet adhesion to fibrinogen, was measured by flow cytometry. Antibody binding in the three type I patients, who exhibited severely defective adhesion, was found to be less than 5%, while that in the two type I patients, who showed 66% and 89% adhesion, was 9% and 24%, respectively.These results demonstrate that the level of GPIIb/IIIa complex on the surface of patient s platelets may account for the residual function of platelet adhesion to fibrinogen in type I thrombasthenia, suggesting the heterogeneity of this congenial disease.