Female factor IX deficiency due to maternally inherited X-inactivation.

X-chromosome inactivation is normally a random event that is regulated by the X chromosome itself. Rarely, females are affected by X-linked disorders from extremely skewed X-chromosome inactivation. Here, we report a family with hemophilia B with female expression through inherited X skewing that appears to be independent of either X chromosome. This finding suggests the possibility of a dominant autosomal contribution to inherited skewed X inactivation.