Combined deficiencies of Factor VIII (AHF) and Factor XI (PTA).

Combined deficiencies of Factor VIII and Factor XI associated with moderate degree of bleeding symptoms were found in 3 brothers. Examination of Factor VIII activity and Factor VIII-related antigen revealed that the Factor VIII activity/Factor VIII-related antigen ratio was significantly decreased in their mother and maternal grandmother consistent with the carrier state of hemophilia. Factor XI deficiency was found in 2 siblings, the father, and 2 of his sisters. The paternal grandmother was thought to carry the abnormal Factor X I gene, although her Factor XI level was normal, because of a significant bleeding history. It was concluded that the combined Factor VIII and XI deficiencies in the 3 brothers represent the coincidental inheritance of 2 separate and independent abnormal genes.