Carrier analysis of a moderately affected haemophilia B family

Here we report the successful genetic diagnosis of a pregnant caucasian fem ale patient whose family has a history of moderate haemophilia B. While res triction fragment length polymorphism (RFLP) analysis was not informative, nucleotide sequencing of the factor IX genes of the patient's family member s determined that her mother and one of her two sisters were carriers of th e mutation C31008T, which causes a Thr296Met transition. In contrast, the p regnant female herself and her other sister were found to carry only normal alleles. Plasma factor IX activity and antigen levels supported these find ings.