Glanzmann’s thrombasthenia is most often an autosomal recessive disease, meaning that both parents must each pass on one mutated allele for the offspring to be affected. Rarely, patients can acquire the disease if they form autoantibodies to their GPIIb/IIIa receptors.
The GPIIb/IIIa receptors anchor platelets to each other by binding fibrinogen on neighboring platelets. Since platelets are unable to clump together, platelet plugs cannot form, and primary hemostasis does not begin. In contrast, Bernard-Soulier syndrome involves the deficiency of the GPIb receptor, which affects the binding of von Willebrand factor to platelets.
Without GPIIb/IIIa receptors on their surface to bind fibrinogen, adjacent platelets are unable to bind to one another and form a platelet plug as part of primary hemostasis. Drugs such as abciximab used for anticoagulation during angioplasty take advantage of this mechanism by blocking GpIIb/IIIa receptors.
Patients with platelet disorders may exhibit mucosal bleeding, which may manifest as epistaxis, hemoptysis, menorrhagia, or gingival and GI bleeds.
Patients with platelet disorders may exhibit easy bruising, petechiae, purpura, and ecchymoses.
Because platelets have difficulty aggregating and forming a platelet plug, patients have a prolonged bleeding time. This test is rarely performed today but is still tested on exams.
Affected patients have a normal platelet count, in contrast to Bernard-Soulier syndrome, in which patients have sparse, enlarged platelets.
NSAIDs non-selectively inhibit cyclooxygenase (COX), an enzyme that produces thromboxane A2, a protein that promotes platelet plug formation. Patients with Glanzmann’s thrombasthenia should not take NSAIDs, as their platelets already are unable to aggregate properly.
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