Two new candidate mutations in type IIA von Willebrand's disease (Arg834-->Gly, Gly846-->Arg) and one polymorphism (Tyr821-->Cys) in the A2 region of the von Willebrand factor.

Recently, several von Willebrand factor gene mutations resulting in type IIA von Willebrand's disease have been reported. We examined 8 patients from Sweden and Denmark with this phenotype and found two new candidate mutations and a hitherto unknown amino acid polymorphism. One patient had a de novo occurring mutation resulting in substitution of glycine for arginine 834. Previous reports have demonstrated conversion of arginine 834 to tryptophan or glutamine in IIA patients. A 2nd patient had a G(4825)-->A transition, substituting arginine for glycine 846. The transition produces a sequence congruent with that of the pseudogene but several lines of evidence indicate that a sequencing error due to influence by the latter could be excluded. The remaining 6 patients had one of the earlier described substitution mutations: Ser743-->Leu and Ile865-->Thr. In addition, two sequence variations not linked to the phenotype were found, namely Tyr821-->Cys and Val802-->Leu.