Haemophilia B
| Haemophilia B | |
|---|---|
| Classification and external resources | |
| Specialty | Haematology |
| ICD-10 | D67 |
| ICD-9-CM | 286.1 |
| OMIM | 306900 |
| DiseasesDB | 5561 |
| MedlinePlus | 000539 |
| eMedicine | emerg/240 |
| Patient UK | Haemophilia B |
| MeSH | D002836 |
Haemophilia B (or hemophilia B) is a blood clotting disorder caused by a mutation of the factor IX gene, leading to a deficiency of factor IX. It is the second-most common form of haemophilia, rarer than haemophilia A. It is sometimes called Christmas disease, named after Stephen Christmas, the first patient described with this disease.[1] In addition, the first report of its identification was published in the Christmas edition of the British Medical Journal.[2]
Contents
Treatment
Treatment (bleeding prophylaxis) is by intravenous infusion of factor IX. Factor IX has a longer half life than factor VIII (deficient in haemophilia A) and as such factor IX can be transfused less frequently.
Genetics
The factor IX gene is located on the X chromosome (Xq27.1-q27.2). It is an X-linked recessive trait, which explains why, as in haemophilia A, usually only males are affected. One in 20,000–30,000 males are affected.
In 1990, George Brownlee and Merlin Crossley showed that two sets of genetic mutations were preventing two key proteins from attaching to the DNA of people with a rare and unusual form of haemophilia B – haemophilia B Leyden – where sufferers experience episodes of excessive bleeding in childhood but have few bleeding problems after puberty.[3] This lack of protein attachment to the DNA was thereby turning off the gene that produces clotting factor IX, which prevents excessive bleeding.[4]
In 2013, Merlin Crossley discovered the third and final protein causing haemophilia B Leyden.[5]
Pathophysiology
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.
European royal families
A study published in 2009 identified the blood disease affecting the royal families of Great Britain, Germany, Russia and Spain as haemophilia B on the basis of genetic markers.[6][7]
See also
References
- ↑ Christmas' disease at Who Named It?
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- ↑ http://ghr.nlm.nih.gov/condition/hemophilia
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- ↑ http://www.biotechlearn.org.nz/news_and_events/news/2013_archive/royal_disease_mystery_solved
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External links
- GeneReviews/NCBI/NIH/UW entry on Hemophilia B
- Hemophilia: What is it? at CSHL Your Genes, Your Health
- hemophilia B at GPnotebook
