Type IIB von Willebrand's disease: unusual response to cryoprecipitate infusion.

A 16-year-old boy had IIB von Willebrand's disease. The disorder is characterized by prolonged bleeding times; normal plasma levels of factor VIII-coagulant activity, factor VIII-ristocetin cofactor activity, and factor VIII-related antigen; abnormal (anodal) mobility of plasma factor VIII-related antigen on two-dimensional crossed immunoelectrophoresis; and enhanced binding of plasma factor VIII-related antigen to normal platelets in the presence of ristocetin. These variables were measured at time periods after an infusion of normal cryoprecipitate into the patient. The electrophoretic mobility of his plasma factor VIII-related antigen was normal 15 minutes after the infusion but became abnormal (anodal) by 4 hours. His bleeding times were normal after 24 hours and did not correlate with plasma levels of factor VIII-coagulation activity, factor VIII-ristocetin cofactor, factor VIII-related antigen, or the electrophoretic mobility of his plasma factor VIII-related antigen. These results imply that the abnormal factor VIII/von Willebrand factor multimers in the plasma of these patients can associate with normal factor VIII/von Willebrand factor multimers and delay the deposition of the normal multimers into subendothelial surfaces. This may require cryoprecipitate infusions 24 hours before elective surgical procedures.