FURTHER-STUDIES ON THE FACTOR-VIII OF A PATIENT WITH A VARIANT FORM OF VONWILLEBRANDS DISEASE

Additional results are presented on a patient previously reported with a variant form of von Willebrand's disease (vWd) with normal levels of factor VIII coagulant activity (VIII-C) and factor VIII-antigen (VIII-Ag) but undetectable von Willebrand factor activity (VIII-vWf). The VIII-C of this patient had normal temperature stability, underwent normal activation in response to thrombin and migrated normally on 2-dimensional immunoelectrophoresis against anti-factor VIII. In contrast to normal plasma, an analysis of the cryoprecipitate and supernate from the patient showed that the VIII-Ag was concentrated in the precipitate. Some evidence was found for a carbohydrate deficiency or abnormality since binding of the lectin concanavalin A (Con A) to the purified factor VIII (FVIII) from this patient was grossly reduced when compared with binding to purified normal FVIII. Rabbit antibodies were prepared against purified normal FVIII and purified patient FVIII and the properties compared. Each antibody formed a precipitating complex with both normal and patient FVIII and both inhibited normal VIII-C and VIII-vWf. Patient FVIII 'blocked' the anti-vWf activity of each antibody to a lesser degree than did normal FVIII and failed to 'block' the anti-VIII-C of either antibody despite normal binding properties of the patient FVIII towards each antibody. It is suggested that the patient's FVIII has a carbohydrate abnormality or deficiency which results in lack of expression of the vWf activity. © 1979.