Distinguishing between type 2B and pseudo-von Willebrand disease and its clinical importance.

Pseudo-von Willebrand disease (p-VWD) and type 2B von Willebrand disease (VWD) have similar phenotypic parameters and clinical symptoms, but different aetiologies. Fourteen individuals from five families with a historical diagnosis of type 2B VWD but with no mutation in the von Willebrand factor gene were re-investigated for the possibility of p-VWD, using platelet aggregation in the presence of cryoprecipitate. p-VWD was confirmed by targeted DNA sequencing of the glycoprotein Ibalpha gene, identifying a heterozygous Glycine 233 Valine substitution. This study suggests that p-VWD may be under diagnosed, and that platelet aggregation in the presence of cryoprecipitate is useful in differentiating this disorder from type 2B VWD.