Case report of two siblings with type 2A von Willebrand disease involving a novel mutation within the calcium-binding site of the A2 domain of von Willebrand factor.

: Calcium-binding at the A2 domain protects von Willebrand factor (VWF) from cleavage by a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS13) and is coordinated by five important residues (p.Asp1596, p.Arg1597, p.