Defective platelet function may present clinically with a variety of symptoms indicative of primary haemostatic failure, such as bruises, ecchymoses, epistaxis, gastrointestinal haemorrhage or menorrhagia. Platelet defects usually give rise to a fairly mild bleeding disorder, and patients may present with exzessive bleeding only after surgery. Inherited disorders of the platelet membrane Glanzmann Thrombasthenia Thrombasthenia was first described by Glanzmann in 1918. Although most patients with this defect have no detectable platelet fibrinogen and absent clot retraction, platelets of some patients contain fibrinogen and can support clot retraction. These criteria were used to classify thrombasthenic patients as type I and II, respectively.
Clinical symptoms occur only in patients homozygous for thrombasthenia.
Platelet aggregation is typically absent in response to all physiologic agonists, such as ADP, collagen, thrombin and epinephrine. Ristocetin-induced binding of vWF to thrombasthenic platelets is normal and aggregation induced by ristocetin and VWF is also initially normal, but it may be reversible. Inherited abnormalities of signal transduction back to the homepage This page was last modified on June 19 1996.