Moderate haemophilia B in a female carrier caused by preferential inactivation of the paternal X chromosome
The case of a female with moderate haemophilia B is reported. She is the only affected member of her family, and factor IX RFLP analysis shows her to have inherited no maternal markers for polymorphisms located in the first intron and 8 Kb 3' of the polyadenylation signal (DdeI and HhaI, respectively). This clearly indicates a deletion involving at least the last 7 exons of the factor IX gene. Her