GP1BA and Thrombocytopenia: The bleeding phenotype in VWD-type 2B is often explained by 1) the unavailability of GPIbα due to constitutively bound VWF 2B mutant 2) the absence of HMW-VWF multimers, the most functionally effective forms of VWF and 3) the moderate-to-severe thrombocytopenia observed in these patients (Fig. 4).