Haemophilia B (also spelled Hemophilia B or Hæmophilia B) is a blood clotting disorder caused by a mutation of the Factor IXgene. 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. Medline abstract (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=12997790) (PMID 12997790).
Diseases affecting trees in their natural settings may be relatively harmless, but in intensively managed nurseries and plantations, they can have a devastating impact (fig.
Winter injury can be distinguished from the needlecast disease by lack of needlespots and fruiting bodies, browning on the entire length of affected needles, and by green foliage on bottom of tree that was protected by snow cover (fig.
The primary disease that affects this native spruce in Christmas tree plantations is Rhizosphaera needlecast.
Christmasdisease, also known as hemophilia B or Factor IX deficiency, is less common than hemophilia A with similar in symptoms.
Christmasdisease, or hemophilia B, is also hereditary but less common than hemophilia A. The severity of Christmasdisease varies from mild to severe, although mild cases are more common.
Christmasdisease will be checked against normal bleeding and clotting time, as well as for abnormal serum reagents in factor IX deficiency.
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