Review Question - QID 107104

Glanzmann’s thrombocytopenia is a congenital platelet disorder in which platelet membranes are deficient in GpIIb/IIIa receptors. Abciximab is a GpIIb/IIIa receptor blocker.

Patients with Glanzmann’s thrombasthenia present with mucocutaneous bleeding at an early age, with symptoms such as menorrhagia, epistaxis, gingival bleeding, and increased post-operative bleeding. Abciximab is a monoclonal antibody that antagonizes IIb/IIIa glycoprotein receptors on activated platelets and prevents platelet aggregation. It is used in the treatment of acute coronary syndromes and in percutaneous transluminal coronary angioplasty. Toxicity includes bleeding and thrombocytopenia.

Ballas et al. summarize the diagnostic work-up in a patient with increased bruising and bleeding. A family and past medical history, specifically a bleeding history, are good first steps. Initial laboratory evaluations should include CBC, blood smear, PT/INR, PTT, and more specialized tests such as platelet function analysis, mixing studies, and inhibitor assays.

Introduction of antiplatelet agents has contributed substantially to improve the outcome of patients with acute coronary syndromes. Dziewierz et al. performed a meta-analysis of the studies on abciximab administration during primary percutaneous coronary intervention (PCI) for acute ST-segment elevation myocardial infarction (STEMI). They confirmed the mortality benefit associated with intravenous bolus and infusion of abciximab compared to placebo.

Illustration A displays the GpIIb/IIIa receptor.

Incorrect Answers:
Answer 2: Aspirin inhibits the platelet COX enzymes.
Answer 3: Warfarin inhibits production of vitamin K-dependent coagulation factors.
Answer 4: Clopidogrel blocks ADP-mediated platelet aggregation via irreversible blockade of ADP receptors.
Answer 5: Cilostazol is a phosphodiesterase III inhibitor, which increases cAMP in platelets.