Heterogeneity of von Willebrand's disease: study of 40 Iranian cases.

Forty Iranian patients with von Willebrand's disease were tested for bleeding time, platelet retention to glass beads, ristocetin-induced platelet aggregation, and assay of factor VIII procoagulant activity (VIII:C), Willebrand factor activity (VIIIR:WF), and factor VIII-related antigen (VIIIR:AG) by two methods (Laurell and immunoradiometric assay). In 22 cases from 11 families, levels of VIII:C, VIIIR:WF and VIIIR:AG (Laurell) were below 5% and the immunoradiometric assay showed total lack of VIIIR:AG in all cases (sensitivity of the method 0.01%). In 10 of these families, the parents were related, raising th;e possibility that these patients are homozygous. The occurrence of precipitating antibodies to factor VIII was demonstrated in one of these severe patients. In seven cases from five families the anomaly was less severe, with results of VIII:C between 5 and 17%. In 11 cases from six families VIII:C was normal or moderately decreased, contrasting with lower levels of VIIIR:WF and VIIIR:AG. The presence of an abnormal factor VIII/von Willebrand factor protein was assessed by double-cross immunoelectrophoresis and gel filtration.