A DE-NOVO TRANSLOCATION 46,X,T(X-15) CAUSING HEMOPHILIA-B IN A GIRL -A CASE-REPORT

Haemophilia B is an X-linked recessive bleeding disorder caused by mut ations in the factor LY gene with an incidence of 1:25 000-30 000. Usu ally female carriers are clinically normal, and severe phenotypic expr ession of the disease in females is extremely rare. In this report we describe a girl with a clinically severe course of haemophilia B who h ad no signs of Turner syndrome or any other dysmorphic features. Cytog enetic and molecular studies in the patient and her parents showed a d e novo translocation 46,X,t(X;15)(q27.1:p11.2) in the patient, indicat ing a possible break near the factor IX gene. The structurally normal X chromosome was late replicating and inactivated in all metaphases as shown by high-resolution R-banding. By fluorescence in situ hybridiza tion (FISH) with YAC and cosmid probes we could further characterize t he breakpoint region on the X chromosome and the involvement of the fa ctor TX gene.