What is the role of combined congenital deficiencies in the etiology of factor IX deficiency (FIX) (hemophilia B)?

Updated: Mar 09, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Srikanth Nagalla, MD, MS, FACP  more...
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Combined congenital deficiencies of vitamin K–dependent factors include reductions in FIX. A mutation in the carboxylase enzyme can lead to a reduction in all Gla-containing proteins, including FIX. Bleeding manifestations depend on the basal level of factors. Patients have a heterogeneous response to oral/parenteral vitamin K administration, varying between a slight response to no response.

Hemophilia B may be associated with other hemostatic defects due to co-inheritance of von Willebrand disease, platelet defects, or other defects, which then compromise hemostasis at multiple sites, thus further accentuating bleeding manifestations in patients with known hemophilia.

Co-inheritance of thrombophilic mutations can ameliorate bleeding in patients with FIX deficiency and can predispose patients to thrombosis when FIX levels are normal and patients are subject to a thrombogenic stimulus.

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