Hemorrhagic diathesis in a carrier of hemophilia B.

A carrier of hemophilia B was found to have an unusually low factor IX level of 13 per cent. Her history of previous bleeding and the hospital course following elective dental extractions were consistent with a mild hemorrhagic diathesis. The patient is a member of a rare kindred of hemophiliacs. The mean level of factor IX in 12 carriers in this kindred was 42 per cent, with a range of 13 to 100 per cent. This patient represents the sixth reported case in which a female carrier of factor IX deficiency was symptomatic.