GP1BA-related Bernard-Soulier syndrome

Any Bernard-Soulier syndrome in which the cause of the disease is a variation in the GP1BA gene, characterized by macrothrombocytopenia, reduced or absent expression of the GPIb-IX-V complex, and lifelong mucocutaneous bleeding. Affected individuals have large platelets with defective ristocetin-induced agglutination, reflecting the absence or dysfunction of GPIbα on the platelet surface. Variants in GP1BA impair production, trafficking, or incorporation of GPIbα into the receptor complex, preventing normal surface assembly and leading to the classic BSS adhesion defect.