Isolated reduced coagulation activity of FVIII may be a manifestation of haemophilia A, carriership of haemophilia A, haemophilia A in a woman, acquired haemophilia A and type 2N of von Willebrand´s disease. The authors were concerned with the cause of isolated reduction of the coagulation activity of factor VIII (19 IU/dl) in a 40-year-old woman with a history of excessive haemorrhage of the type of mild haemophilia A with a negative family history. The personal history, family history and laboratory examination suggested type (variant) 2N of von Willebrand ´s disease. For indirect evidence the authors used a therapeutic study where they investigated the effect of administration of a concentrate of coagulation factors VIII/von Willebrand´s factor (1/2), 28 IU factor VIII/kg body weight, on the coagulation activity of factor VIII. They recorded a half-life prolonged to 53 hours as compared with controls where the half-life was less than 12 hours. The therapeutic study confirmed sufficient coagulation activity of factor VIII, the utilization of which improved as a result of administration of von Willebrand´s factor. This investigation confirmed indirectly as the cause of reduced coagulation activity of factor VIII in the examined patient the assumed type (variant) 2N of von Willebrand´s disease.

        Key words: Von Willebrand´s factor - Von Willebrand´s disease - von Willebrand´s disease type 2N