[Congenital anomalies of the human blood platelet, models for understanding mechanisms of platelet secretion: gray platelet disease].

The fundamental role of different platelet glycoproteins and proteins in platelet function is well known. Glycoproteins II b and III a, missing from platelets of patients with Glanzmann's thrombasthenia, appear to play a role in the mechanism of platelet cohesion. Platelet adhesion to sub-endothelium components depends on the binding of von Willebrand factor to the platelet membrane and this is defective in the Bernard Soulier syndrome which is characterised by the absence from the platelets of membrane glycoprotein Ib. The gray platelet syndrome is a new platelet disorder characterized by the absence of alpha granules and a reduced platelet aggregation response associated with an abnormal dense body section. Analysis of the protein and glycoprotein content of gray platelets has shown that they lack or have markedly reduced concentrations of the alpha granule proteins. It would appear that proteins secreted from the alpha granules may play a role during the later stages of platelet secretion leading to platelet aggregation.