SEEMING HOMOZYGOSITY IN TYPE-IIB VON WILLEBRANDS DISEASE DUE TO A POLYMORPHISM WITHIN THE SEQUENCE OF A COMMONLY USED PRIMER

In an isolated type-IIB von Willebrand's disease patient we detected a Val(553)->Met substitution. The patient seemed to be homozygous, alth ough this substitution was absent in both asymptomatic parents. Since two identical de novo mutations are highly unlikely, we tested for uns uccessful amplification of one allele. We found a novel polymorphism i n the complementary sequence of a primer widely used for selective amp lification of the von Willebrand factor gene.