Von Willebrand's syndrome. Studies on a variant factor VIII.

A girl with symptoms of von Willebrand's disease was found to have a slightly reduced or normal FVIII procoagulant activity, normal FVIII-related antigen (VIIIR:AG) and virtually absent von Willebrand's factor. The electrophoretic mobility of the VIIIR:AG in this patient's plasma and plasma fractions was increased and has been compared with that of two reported patients with FVIII variants. Her lysed platelets contained increased amounts of VIIIR:AG which had an increased anodal migration identical to her plasma VIIIR:AG. Experiments involving the selective absorption of a rabbit antiserum with the patient's plasma provide evidence that VIIIR:AG and von Willebrand's factor are immunologically distinct.