Hemophilia B - Definition and Overview

Haemophilia B (also spelled Hemophilia B or Hæmophilia B) is a blood clotting disorder caused by a mutation of the Factor IX gene. It is the second most common form of haemophilia, but rarer than haemophilia A. It is sometimes called Christmas disease after Stephen Christmas, the first patient described with this disease. In addition, the first report of its identification was published in the Christmas edition of the British Medical Journal. Treatment (bleeding prophylaxis) is by infused factor IX.

Genetics and pathophysiology

The factor IX gene is located on the X chromosome (Xq27.1-q27.2). It is inherited X-linked recessive, which explains why - as in haemophilia A - only males are generally affected.

Factor IX deficiency leads to an increased propensity for haemorrhage. This is in response to mild trauma or even spontaneously, such as in joints (haemarthrosis) or muscles.

Reference

• Biggs RA, Douglas AS, MacFarlane RG, Dacie JV, Pittney WR, Merskey C, O'Brien JR. Christmas disease: a condition previously mistaken for haemophilia. Br Med J 1952;2:1378-1382. PMID 12997790.

External links

• OMIM 306900 (http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=306900)
• Your genes your health (http://www.yourgenesyourhealth.org/ygyh/mason/ygyh.html?syndrome=hemo&section=whatisit&video=0) page on Haemophilia B.