Type 2N von Willebrand disease.

Type 2N von Willebrand disease (VWD) refers to patients with a factor VIII (FVIII) deficiency caused by a markedly decreased affinity of von Willebrand factor (VWF) for FVIII. It is inherited as an autosomal recessive trait but is clinically similar to mild hemophilia. The differential biologic diagnosis, which is of major importance for providing relevant genetic counseling and optimal treatment, is based on the measurement of plasma VWF capacity to bind FVIII. Molecular biology techniques have allowed the identification of 20 missense mutations in the VWF gene that cause type 2N VWD. All of them induce changes in amino acid residues located in the N-terminal part of mature VWF, which contains the FVIII binding site. Their identification may provide a genetic diagnosis. Theoretically, patients with type 2N VWD should be treated with products containing VWF that is able to stabilize their endogenous normal FVIII.