GP1BA and von Willebrand disease (hereditary or acquired): Among VWD, VWD-2B is characterized by gain-of-function mutations in the VWF-A1 domain, which promote constitutive binding of mutant VWF to GPIbα.[3, 4] The bleeding tendency observed in these patients is often explained by the absence of high molecular weight VWF multimers, as well as to the unavailability of GPIbα due to constitutively bound 2B mutants and finally to thrombocytopenia.