Hemophilia B

Haemophilia B
X-linked recessive inheritance
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. Haemophilia B was first recognized as a different kind of haemophilia in 1952. It is sometimes called Christmas disease, named 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.

The presentation of hemophilia B is consistent with easy bruising, urinary tract bleed and nosebleeds. Additionally, the affected individual may experience bleeding into their joints.

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.

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. This lack of protein attachment to the DNA was thereby turning off the gene that produces clotting factor IX, which prevents excessive bleeding.

...
Wikipedia