Hemophilia B is a hemorrhagic disease characterized by a deficiency of factor Ⅸ
activity and a sex-linked recessive mode of inheritance, and is clinically indistinguishable
from hemophilia A.
Four cases of proven hemophilia B are presented with a brief review of the literature.
The first case (M 1-l/2 yr.) was associated with idiopathic thrombocytopenic purpura,
and plasma factor Ⅸ level was 0.3% of normal. The second (M 20yr.) and the third (M
24yr.) cases were siblings, with 1.0% and 0.7% of factor Ⅸ activity. Family study of
these second and third cases showed that their father had subhemophilic level of factor
Ⅸ activity (35%), and their mother, an obligatory carrier, and their sister, a potential
carrier, had reduced factor Ⅸ levels, 48% and 35% respectively. The fourth case (M 18
yr.) had 3.2% of factor Ⅸ activity.
The authors believe that this is the first report of factor assay-proven cases of
hemophilia B in the Korean literature.
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