A practical approach to genetic testing for von Willebrand disease.

von Willebrand disease (vWD) is the most commonly diagnosed congenital bleeding disorder. The laboratory diagnosis of type 2 variants and type 3 vWD is reasonably well defined, and characterization of the von Willebrand factor (vWF) gene has facilitated definition of their molecular basis. However, for type 1 vWD, the laboratory diagnosis poses a diagnostic dilemma, and knowledge of its molecular basis is evolving. Characterization of the vWF gene and refinement of genetic techniques have led to an evolving repertoire of genetic tests. Genetic testing is costly, and thus judicious use will be increasingly important for appropriate genetic-counseling of patients with vWD and their family members. This article provides a practical approach to utilization of genetic testing in vWD.