factor IX deficiency
X-linked bleeding disorder caused by deficient or dysfunctional coagulation factor IX, also known as hemophilia B.
Full Definition
Factor IX deficiency, also known as hemophilia B or Christmas disease, is an X-linked recessive bleeding disorder caused by mutations in the F9 gene leading to deficient or dysfunctional factor IX protein. The condition affects approximately 1 in 30,000 male births and is clinically indistinguishable from hemophilia A, presenting with bleeding into joints, muscles, and other organs. Severity correlates with residual factor IX activity levels: severe (<1%), moderate (1-5%), or mild (5-40%). Treatment involves factor IX replacement therapy, with newer options including extended half-life products and gene therapy.
Usage
Usage note: Use Roman numeral IX. Specify severity level when known. Hemophilia B is acceptable alternative term.
In Context
- "Genetic testing confirmed severe factor IX deficiency with a nonsense mutation in exon 7." — Genetics consultation
- "The patient's factor IX level was 2%, consistent with moderate hemophilia B." — Coagulation laboratory report