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Glanzmann Thrombasthenia
Glanzmann thrombasthenia (GT) is an autosomal-recessive platelet function disorder in which platelet appearance and platelet number are unaffected. Patients with GT present with platelet-type bleeding, which may be severe, such as purpura, epistaxis, oral mucosal bleeding, menorrhagia, or gastrointestinal bleeding.
Pathophysiology
The most common genetic cause of GT is mutations in both alleles of one of the genes that encode for the α IIb or β 3 polypeptide of the platelet integrin receptor α IIb β 3 . α IIb β 3 is the integrin receptor that mediates platelet adhesion to fibrinogen and von Willebrand factor and is normally expressed at high levels on the platelet surface. In the absence of functional α IIb β 3 , both platelet adhesion and platelet recruitment, or aggregation, are markedly impaired.
The majority of causative mutations in patients with GT result in severely decreased platelet surface expression of α IIb β 3 . Mutations in the α IIb or β 3 component result in a similar phenotype. Reported mutations include point mutations, splice defects, and small deletions and gene inversions.
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