Haemophilia or hemophilia (from Greek haima "blood" and philia "to love"[1]) is the name of a family of hereditary genetic disorders that impair the body's ability to control blood clotting, or coagulation. In the most common form, haemophilia A, clotting factor VIII is absent. Hemophilia B, also known as factor IX deficiency, is the second most common type of hemophilia, but Hemophilia B is far less common than Hemophilia A. Occurring in about one in 25,000 male births.[2]

The effects of this sex-linked, X chromosome disorder are manifested almost entirely in males, although the gene for the disorder is inherited from the mother. In about 30% of cases of Hemopilia B, however, there is no family history of the disorder and the condition is the result of a spontaneous gene mutation. [3] A mother who is a carrier also has a 50% chance of giving the faulty X chromosome to her daughter. That does not give the daughter the hemophilia disease, but it does result in the daughter becoming a hemophilia carrier. Females are almost exclusively asymptomatic carriers of the disorder, and may have inherited it from either their mother or father.

These genetic deficiencies may lower blood plasma clotting factor levels of coagulation factors needed for a normal clotting process. When a blood vessel is injured, a temporary scab does form, but the missing coagulation factors prevent fibrin formation which is necessary to maintain the blood clot. Thus a haemophiliac does not bleed more intensely than a normal person, but for a much longer amount of time. In severe haemophiliacs even a minor injury could result in blood loss lasting days, weeks, or not ever healing completely. The critical risk here is with normally small bleeds which due to missing factor VIII take long times to heal. In areas such as the brain or inside joints this can be fatal or life debilitating.

The bleeding with external injury is normal, but incidence of late re-bleeding and internal bleeding is increased, especially into muscles, joints, or bleeding into closed spaces. Major complications include hemarthrosis, hemorrhage, gastrointestinal bleeding, and menorrhagia.