Heightened proteolysis of the von Willebrand factor subunit in patients with von Willebrand disease hemizygous or homozygous for the C2362F mutation

We studied the proteolytic pattern of the mutant von Willebrand factor (VWF) in four patients with von Willebrand disease (VWD) who were either homozygous or hemizygous for the mutation C2362F. A significant decrease in the native fragment of 225 kDa was evident in all the patients, together with a marked increase in the 176 and 140 kDa fragments, a pattern usually observed in type 2A VWD. The proteolytic pattern measured in four heterozygotes for C2362F was within the normal range, suggesting that the mutant VWF C2362F present in the plasma of these patients may be protected from proteolysis by normal VWF.