Glanzmann thrombasthenia (GT) is an autosomal dominant coagulation disorder that results in spontaneous, prolonged, or heavy bleeding that can be life-threatening. It is caused by mutations in the ITGA2B or ITGB3 gene that result in defective or deficient platelet alpha IIb beta 3 integrin (formerly known as glycoprotein llb/llla), which is the platelet fibrinogen receptor. The functionality of this receptor is necessary for platelet aggregation. Acquired GT, on the other hand, is due to autoantibodies against alpha IIb beta 3 integrin.

Signs and symptoms include manifestations of mucocutaneous bleeding such as epistaxis, menorrhagia, petechiae, easy bruising, hematoma, and rarely intracranial hemorrhage or hematuria. Family history of bleeding is common.