Haemophilia B
Encyclopedia
Haemophilia 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 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
.
(Xq27.1-q27.2). It is an X-linked recessive trait, which explains why, as in haemophilia A, only males are usually affected. 1 in 50,000 males are affected.
) or muscles.
Coagulation
Coagulation is a complex process by which blood forms clots. It is an important part of hemostasis, the cessation of blood loss from a damaged vessel, wherein a damaged blood vessel wall is covered by a platelet and fibrin-containing clot to stop bleeding and begin repair of the damaged vessel...
disorder caused by a mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...
of the Factor IX
Factor IX
Factor IX is one of the serine proteases of the coagulation system; it belongs to peptidase family S1. Deficiency of this protein causes hemophilia B. It was discovered in 1952 after a young boy named Stephen Christmas was found to be lacking this exact factor, leading to...
gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
, leading to a deficiency of Factor IX. It is the second most common form of haemophilia
Haemophilia
Haemophilia is a group of hereditary genetic disorders that impair the body's ability to control blood clotting or coagulation, which is used to stop bleeding when a blood vessel is broken. Haemophilia A is the most common form of the disorder, present in about 1 in 5,000–10,000 male births...
, rarer than haemophilia A
Haemophilia A
Haemophilia A is a deficiency in clotting factor VIII.Haemophilia A is inherited as an X-linked recessive trait, and thus occurs in males and in homozygous females. However, mild haemophilia A has been described in heterozygous females, presumably due to extremely unfavourable lyonization...
. It is sometimes called Christmas disease after Stephen Christmas
Stephen Christmas
Stephen Christmas was the first patient described to have Christmas disease in 1952 by a group of British doctors.-Biography:...
, 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
British Medical Journal
BMJ is a partially open-access peer-reviewed medical journal. Originally called the British Medical Journal, the title was officially shortened to BMJ in 1988. The journal is published by the BMJ Group, a wholly owned subsidiary of the British Medical Association...
.
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 chromosomeX chromosome
The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...
(Xq27.1-q27.2). It is an X-linked recessive trait, which explains why, as in haemophilia A, only males are usually affected. 1 in 50,000 males are affected.
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 (haemarthrosisHemarthrosis
Hemarthrosis is a bleeding into joint spaces.-Causes:It usually follows injury but occurs mainly in patients with a predisposition to hemorrhage such as those being treated with warfarin and patients with hemophilia.It can be associated with knee joint arthroplasty.-Treatment:In hemophilia it may...
) 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.See also
- HaemophiliaHaemophiliaHaemophilia is a group of hereditary genetic disorders that impair the body's ability to control blood clotting or coagulation, which is used to stop bleeding when a blood vessel is broken. Haemophilia A is the most common form of the disorder, present in about 1 in 5,000–10,000 male births...
- Haemophilia AHaemophilia AHaemophilia A is a deficiency in clotting factor VIII.Haemophilia A is inherited as an X-linked recessive trait, and thus occurs in males and in homozygous females. However, mild haemophilia A has been described in heterozygous females, presumably due to extremely unfavourable lyonization...
- Haemophilia CHaemophilia CHaemophilia C is a mild form of haemophilia affecting both sexes. However, it predominantly occurs in Jews of Ashkenazi descent. It is the fourth most common coagulation disorder after von Willebrand's disease and haemophilia A and B...
- Haemophilia in European royaltyHaemophilia in European royaltyHaemophilia figured prominently in the history of European royalty in the 19th and 20th centuries. Britain's Queen Victoria, through two of her five daughters , passed the mutation to various royal houses across the continent, including the royal families of Spain, Germany and Russia. Victoria's...
External links
- GeneReviews/NCBI/NIH/UW entry on Hemophilia B
- Hemophilia: What is it? at CSHLCold Spring Harbor LaboratoryThe Cold Spring Harbor Laboratory is a private, non-profit institution with research programs focusing on cancer, neurobiology, plant genetics, genomics and bioinformatics. The Laboratory has a broad educational mission, including the recently established Watson School of Biological Sciences. It...
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