Investigation of a case of subtype IIC von Willebrand disease: characterization of the variability of this subtype.

A variant of von Willebrand disease (vWD) has been identified in a 19-year-old woman with a severe bleeding syndrome. She had a very prolonged bleeding time (over 20 min), 24 U/dl factor VIII coagulant activity (F.VIII:C), 16 U/dl von Willebrand factor antigen (vWF:Ag), no ristocetin cofactor activity, and an anodal mobility of vWF:Ag on crossed immunoelectrophoresis (CIE). vWF:Ag was markedly reduced in her platelet lysate. In plasma and platelets, SDS-agarose electrophoresis consistently demonstrated the absence of large multimers, a relatively increased concentration of the fastest-moving multimer, and gross abnormalities of the internal structure of each vWF multimeric unit. Five members from the maternal side of the family had a double vWF:Ag peak by CIE and a relative increase of the fastest-moving vWF multimer by SDS-agarose electrophoresis; no quantitative or qualitative vWF defects were found in the paternal side of the family. The pattern of the findings in the propositus and her family is similar to those of type IIC vWD. However, there are some unique characteristics suggesting phenotypic variability in this subtype, such as low level of platelet vWF:Ag and the absence of increase of vWF after DDAVP administration.