Mild haemophilia B (Q89214)

Mild haemophilia B is a form of haemophilia B characterised by a small deficiency of factor IX leading to abnormal bleeding as a result of minor injuries, or following surgery or tooth extraction. Mild haemophilia B accounts for around 30% of all cases of haemophilia B. The biological activity of factor IX is between 5 and 40%. Spontaneous haemorrhages do not occur. Transmission is X-linked recessive and the disorder is caused by mutations in the F9 gene (Xq28) encoding coagulation factor IX.