GP1BB-related Bernard-Soulier syndrome

Any Bernard-Soulier syndrome caused by deficiency or dysfunction of GPIbβ, leading to markedly decreased GPIb-IX-V surface expression and impaired platelet adhesion. Platelets are enlarged and poorly responsive to ristocetin, consistent with severe reduction of the assembled receptor complex. Variants in GP1BB affect production or proper folding of the GPIbβ subunit, preventing formation of the full receptor complex and resulting in the characteristic Bernard-Soulier phenotype.