The authors present a clinical description, detailed platelet function analysis, and certain biochemical parameters in two siblings with Glanzmann thrombasthenia (G. t.). The isolated occurrence of this disorder in the family corresponds with its autosomal recessive inheritance. In both cases blood platelets completely failed to aggregate. In contrast, the platelet interaction with ristocetin, reflecting their ability to adhere to the subendothelium, the so-called "shape change", the storage granule contents and their release and arachidonic acid metabolism were unaffected. Further, the aggregation abnormality was accompanied by marked procoagulant activity and clot retraction defects; these functions, similarly as aggregation, are implemented on the platelet surface. The analysis of blood platelet proteins, using two dimensional polyacrylamide electrophoresis, confirmed the absence of glycoprotein GP IIb and IIIa and a decrease of the fibrinogen content. The analysis of these findings in G. t. led to the contemporary concept that GP IIb and IIIa on the platelet surface act as receptors for platelet aggregation.

Keywords: Adult; Blood Platelets /chemistry/; Cell Membrane /chemistry/; Female; Humans; Male; Platelet Aggregation; Platelet Membrane Glycoproteins /analysis/; Thrombasthenia /blood/