Bernard-Soulier syndrome is caused by the deficiency of
**Core Concept**
Bernard-Soulier syndrome (BSS) is a rare inherited bleeding disorder characterized by thrombocytopenia, giant platelets, and prolonged bleeding time. It results from a deficiency of the glycoprotein (GP) IIb-IX-V complex, which plays a crucial role in platelet adhesion and aggregation.
**Why the Correct Answer is Right**
The GP IIb-IX-V complex is essential for platelet function, as it serves as the receptor for fibrinogen and von Willebrand factor, allowing platelets to aggregate and form a hemostatic plug. In BSS, the deficiency of this complex impairs platelet function, leading to the characteristic symptoms of the disease. The GP IIb-IX-V complex is a heterotrimeric complex composed of three subunits: GP IIb, GP IX, and GP V.
**Why Each Wrong Option is Incorrect**
**Option A:** VWF deficiency is associated with von Willebrand disease, a distinct bleeding disorder characterized by impaired platelet adhesion.
**Option B:** GPIa/IIa (CD31/CD41) is a different glycoprotein complex involved in platelet adhesion, but its deficiency is not associated with Bernard-Soulier syndrome.
**Option C:** GPIb-IX-V is the correct answer, but it's not listed as an option here.
**Clinical Pearl / High-Yield Fact**
Bernard-Soulier syndrome is often associated with thrombocytopenia, giant platelets, and a prolonged bleeding time, but it's essential to note that the platelet count may be normal in some cases. A thorough laboratory investigation, including flow cytometry and platelet function studies, is necessary to diagnose BSS.
**Correct Answer:** GPIb-IX-V