Whilst haemophilia and Willebrand disease are the most common coagulation disorders, there are other rarer coagulation disorders linked to a deficiency of one of the factors in the coagulation cascade. These deficits can affect both men and women.

Coagulation factors are proteins that circulate inactively in the blood. They are activated and play a procoagulant role as soon as a lesion appears in the vessel. When a coagulation factor is missing or malfunctioning, the coagulation cascade is slowed or even blocked: the blood clot does not form and the bleeding lasts longer than it should. In addition to haemophilia A, caused by a factor VIII deficiency, and haemophilia B, linked to a factor IX deficiency, there are “rare” coagulation disorders, characterised by the absence or defective functioning of one or more factors I, II, V and VIII, VII, X, XI and XIII.

Factor I

Factor I or fibrinogen deficiency is a very rare hereditary disease with complications that can vary according to the severity of the disease.

Fibrinogen, also known as factor I, is a blood plasma protein produced by the liver and playing an important role in blood clotting.

When there is a problem with fibrinogen (either there is a lack of it or it malfunctions), clot formation becomes more difficult. There may be haemorrhage or thrombosis.

Factor II

Factor II deficiency (hypoprothrombinaemia, prothrombin deficiency or FII deficiency) is a rare coagulation disorder. FII is an important blood protein which enables normal blood coagulation.

This protein plays a role in the complex process of coagulation, which prevents the flow of blood through damaged blood vessels. As soon as a vessel ruptures, the elements responsible for coagulation bind together to form a sort of plug at the site of the rupture. Coagulation factors are required to hold the plug in place and form a solid, stable clot that will allow complete healing.

Factor V

Factor V deficiency, also known as pseudohaemophilia or Owren’s disease, is a very rare coagulation disorder. Approximately one person in a million may suffer from this disability. To date, only 150 cases have been identified worldwide. Factor V is a blood protein which plays a role in the coagulation cascade, i.e. the chain reaction triggered when a blood vessel is damaged.

Combined factor V and VIII deficiency

Combined factor V and factor VIII deficiency is very rare. In all, fewer than 100 people, belonging to around sixty families, have been identified worldwide to date.

Factors V and VIII are blood proteins which both play a role in the coagulation cascade reaction. It is an autosomal recessive disorder. This means that both parents must carry the defective gene in order to pass it on to their children.

Factors VII, X, XI and XIII

• Factor VII deficiency is an inherited blood coagulation disorder. It is transmitted from parent to child at the moment of conception. The disease is caused by an abnormal gene. In the case of factor VII deficiency, one of the genes on chromosome 13 is defective.
• Factor X deficiency is an extremely rare blood coagulation disorder, which can present a variety of complications depending on the severity of the disease. Factor X is a protein present in the blood. This protein plays an important role in the coagulation cascade. It is an autosomal recessive disorder.
• Factor XI deficiency is a very rare disease that affects blood coagulation. For reasons that remain unexplained, the tendency to bleed is not always directly proportional to the level of factor XI in the blood. Unlike classical haemophilia (factor VIII deficiency), which tends to affect boys, factor XI deficiency has no gender predilection and affects both girls and boys. The factor XI deficiency gene is located on chromosome 4.
• Factor XIII deficiency is an inherited blood coagulation disorder. Factor XIII is a protein made up of two parts. The first is produced in the bone marrow and the second in the liver. The defective gene in factor XIII deficiency is located on a chromosome that is not responsible for the sex of the child.

Patients with these rare deficiencies are diagnosed and treated in haemophilia treatment centres.