抄録
Two cases in a family with von Willebrand's disease which revealed an increased ristocetin-induced platelet aggregation (RIPA) and a qualitative abnormality of the factor VIII protein are herein reported. The proband was a 5 year old girl with prolonged bleeding time, factor VIII procoagulant activity (VIII: C) of 45∼54%, factor VIII related antigen (VIII R: AG) of 50∼110% and von Willebrand factor activity (VIII R: WF) of 18∼35%. Her father showed almost the same results as the proband in his hemostatic evaluation. The threshold concentration of ristocetin giving 30% increase in light transmission was 0.5 mg/ml in the proband and 0.4 mg/ml in her father (normals: 1.16±SD 0.18 mg/ml). The amount of VIII R: AG in their platelets were normal, but an increased binding affinity of platelets to plasma factor VIII was demonstrated.
The qualitative abnormality of the factor VIII protein was characterized by an increased anodal migration of VIII R: AG on crossed immunoelectrophoresis, a retarded elution pattern as demonstrated by gel filtration on Sepharose 2B and a reduced precipitation with concanavalin A. In both patients a recovery of VIII R: AG to the cryoprecipitate was also reduced.
The responses to factor VIII concentrates and DDAVP were also investigated.
