Moderately severe haemophilia B (Q89199)

Moderately severe haemophilia B is a form of haemophilia B (see this term) characterised by factor IX deficiency leading to abnormal bleeding as a result of minor injuries, or following surgery or tooth extraction. Moderately severe haemophilia B accounts for around 30% of all cases of haemophilia B. The biological activity of factor IX is between 1% and 5%. Spontaneous haemorrhages are rare. Transmission is X-linked recessive and the disorder is caused by mutations in the F9 gene (Xq28) encoding coagulation factor IX.