Review Question - QID 213580

This patient with superficial bleeding, an elevated bleeding time, a normal platelet count, and normal platelet morphology on peripheral blood smear most likely has Glanzmann thrombasthenia. This disease is caused by a mutation in glycoprotein IIb/IIIa.

Glanzmann thrombasthenia is caused by a genetic mutation in the platelet aggregation receptor glycoprotein IIb/IIIa. This mutation causes a defect in platelet quality but not in platelet quantity. Like all platelet disorders, it will present with superficial bleeding such as nosebleeds, petechiae, and purpura, which will be accompanied on laboratory testing with a prolonged bleeding time or platelet function analyzer test. Notably, this disorder will have a normal platelet count, prothrombin time, and partial thromboplastin time. Finally, the morphology of the platelets on peripheral blood smear will be normal in this disease.

Incorrect Answers:
Answer 1: Decreased levels of von Willebrand factor is incorrect because this disease would present with an elevated partial thromboplastin time. This occurs because von Willebrand factor stabilizes coagulation factor VIII.

Answer 2: Mutation in glycoprotein Ib is incorrect because this is the cause of Bernard-Soulier syndrome, which results in enlarged platelet morphology on peripheral blood smear.

Answer 4: Production of anti platelet antibodies is incorrect because in immune thrombocytopenia the platelet count would be decreased.

Answer 5: Production of antibodies against ADAMTS13 is incorrect because in thrombotic thrombocytopenic purpura the platelet count would be decreased.

Bullet Summary:
Glanzmann thrombasthenia is caused by a mutation in the glycoprotein IIb/IIIa receptor on platelets.