Summary
In this paper, a five generation Greek family is described with haemophilia B. The
disease is characterized by a normal ox-brain prothrombin time, normal levels of the
vitamin-K dependent clotting factors VII and X and a proportional reduction of factor
IX acttivity and antigen levels all of which is consistent with the cross-reacting
material negative form of haemophilia B. However, in this family the factor IX levels
in the three patients of generation V are around 1 U/dl while the three older patients
in generation III have factor IX levels ranging from 28 to 44 U/dl. In the oldest
patient of generation V we observed a rise of the factor IX level from 1 U/dl up to
the age of 13 to 10 U/dl at age 14. In addition, the older patients have very mild
bleeding symptoms or none at all, while the young ones have occasional spontaneous
haemorrhages in muscles and joints, compatible with severe or moderately severe haemophilia.
The disease appears to be similar to haemophilia B Leyden which has been described
in a Dutch family.
Key words
Haemophilia B - Puberty - Factor IX - Coagulation factors Summary
