User:Mr. Ibrahem/Haemophilia B

Haemophilia B, also known as Christmas disease, is a bleeding disorder that occurs due to a genetic mutation. Symptoms include easy bruising and bleeding. Complications can include bleeding into joints or the brain. Depending on the severity, the disease may become apparent between the newborn period and adulthood.

It is generally due to an inherited mutation, which occurs in an X-linked recessive pattern. About a third of cases occur due to a new mutation. Rarely it may occur later in life due to the production of antibodies against factor IX. The underlying mechanism involves a lack of factor IX, a part of the coagulation cascade. Diagnosis may be suspected based on a blood test for aPTT and confirmed by a factor IX activity level. It is divided into mild, moderate, and severe depending on a person's factor IX levels.

Treatment is with factor IX concentrate, with recombinant factor IX products often recommended. These may be used preventatively or when bleeding occurs. Fresh frozen plasma may be used if this is not available. Aminocaproic acid may also be used. Gene therapy, in the form of etranacogene dezaparvovec, became an option in the United States in 2022. Despite availability of treatment life expectancy is reduced by about 25%; though, without treatment many died around the age of 12.

Haemophilia B affects about 1 in 25,000 male newborns. Males are primarily affected; though, a few females may also have the disease. It is about 5 times less common than haemophilia A. It was first recognized as a distinct disease in 1952. Many members of European royal families were affected as Queen Victoria carried the mutation.