A new candidate missense mutation (Leu 1657 IIe) in an apparently asymptomatic type 2A (phenotype IIA) von Willebrand disease family

Type 2A von Willebrand disease (VWD) is mostly an autosomal dominantly inhe rited bleeding disorder characterised by a qualitative defect of von Willeb rand factor (VWF), Mutation screening was used to screen the whole of VWF g ene followed by direct sequencing to detect the mutation in a father and so n diagnosed with type 2A (phenotype IIA) von Willebrand disease. A C5219 to A transversion was detected predicting Leucine to Isoleucine substitution in codon 1657. This novel missense mutation which was also identified by Mb oI restriction enzyme analysis, was found in both patient and his father bu t not in any other unaffected family member or 50 unrelated normal individu als. This substitution was reproduced by in vitro site directed mutagenesis of full-length VWF cDNA and transiently expressed in COS-7 cells. The corr esponding recombinant VWF protein exhibited the full spectrum of VWF multim ers, suggesting that the abnormal multimer seen in the patient results from increased proteolysis.