Hemophilia is a congenital bleeding disorder characterized by a deficiency or functional defects of coagulation factor VIII (FVIII), called hemophilia A, or factor IX (FIX), called hemophilia B. The factor deficiencies are the result of mutations in the FVIII or FIX clotting factor genes. Hemophilia A is much more common than hemophilia B – estimated 80-85% of all hemophilia cases. Estimated prevalence at birth is 24.6/100 000 males for hemophilia A and 5/100 000 males for hemophilia B.
Traditionally, hemophilia A and B have been considered clinically indistinguishable. There is some evidence that severe FIX deficiency may be clinically milder than the corresponding degree of FVIII deficiency. Several possible explanations for differences in disease severity can be hypothesized – genetic defects, associated prothrombotic abnormalities, clotting factor characteristics, etc.
In conclusion, despite the clinical indistinguishability of the two diseases, some phenotypic differences are observed in hemophilia B, which require further investigation of the underlying mechanisms. Read the full article here.