Identification of a missense mutation (p.Leu1733Pro) in the A3 domain of von Willebrand factor in a family with type 2M von Willebrand disease.

The proband's von Willebrand factor (VWF) antigen and VWF collagen-binding capacity were 14% and 10%, respectively; his sister's were 16% and 9%, respectively; and his nephew's were 30% and 15%, respectively. No apparent loss of high-molecular weight VWF multimers was observed in the plasma of these patients. A single-nucleotide substitution of T to C was found at nucleotide position 113042 in their VWF gene, converting Leu1733 to Pro in the A3 domain. These results suggest that p.Leu1733Pro is responsible for type 2M von Willebrand disease in this family.