An Abnormal Platelet Glycoprotein Pattern in Three Cases of Glanzmann's Thrombasthenia

S ummary . A glycoprotein abnormality in membrane fractions isolated from the platelets of patients with Glanzmann's thrombasthenia is described. Glycoproteins solubilized from thrombasthenic and control human platelets have been compared by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. Whereas in a control human platelet membrane fraction three major glycoproteins of molecular weight 155 000, 135 000 and 103 000 were observed, in a similar fraction from thrombasthenic platelets a glycoprotein of 152 000 molecular weight predominated. No differences were observed in the nature of a high molecular weight acidic glycopeptide released from washed thrombasthenic and control platelet suspensions by trypsin, and the sialie acid content of thrombasthenic platelets was shown to be within the normal range. It is suggested that the glycoprotein abnormality may be due to an altered organization within the thrombasthenic platelet membrane and that further studies are necesasry to investigate the role of membrane glycoproteins in platelet function.