Types of hemophilia and other bleeding disorders are defined by which clotting factor (or factors) is too low or ineffective in the body. In some cases, hemophilia types are also defined by what causes the bleeding disorder. Knowing which type of bleeding disorder a person has is necessary to ensure effective treatment.
Bleeding disorders are genetic conditions unless otherwise specified. In most types, severity is based on the level of clotting factor activity; lower levels of factor activity usually mean more severe disease.
The most common of all bleeding disorders is von Willebrand disease (VWD). People living with VWD lack von Willebrand factor and can have low levels of factor VIII. One in 100 people may have a form of VWD.
There are three subtypes of von Willebrand disease that describe severity: type 1, type 2, and type 3. Type 1 is the mildest and most common, involving low levels of factor and accounting for as many as 75 percent of cases. In type 2, clotting factors may or may not be low, but they do not work effectively. Type 2 may account for 20 percent to 25 percent of cases and has several subtypes. In type 3 von Willebrand disease — the most severe type — clotting factor may be almost nonexistent. Only 1 in 1 million people have type 3 VWD.
In hemophilia A, also known as classic hemophilia, people lack factor VIII. About 1 in 5,000 males have hemophilia A. About 60 percent of people with hemophilia A have the most severe form of the disease.
People with hemophilia B — also called Christmas disease —lack factor IX. About 1 in 25,000 males have hemophilia B. About 60 percent of people with hemophilia B have the most severe form of the disease. Hemophilia B Leyden, a rare form that affects 3 percent of those with hemophilia B, causes a pattern of bleeding episodes in childhood that subsides after puberty. People with hemophilia B Leyden have extremely low levels of factor IX in childhood that gradually increase as they age. As adults, some people with hemophilia B Leyden reach near-normal levels of factor and may no longer require treatment for their bleeding disorder.
Some people are not born with congenital hemophilia but develop it later in life as a result of another health condition or a medication. Acquired hemophilia, which can be very severe, affects between 1 and 1.5 people per 1 million. Unlike most other types of bleeding disorders, acquired hemophilia can sometimes go away if the underlying problem — health condition or medication — is resolved.
Factor I deficiency is a collection of disorders called congenital fibrinogen defects. Mild cases of factor I deficiency affect about 1 in 1 million people. The severe form, afibrogenemia, affects about 5 in 10 million.
Factor II deficiency affects approximately 1 in 2 million. Factor II deficiency, also referred to as prothrombin deficiency, may be inherited or acquired due to liver disease, lack of vitamin K, or the effects of blood thinner medications. Factor II deficiency is usually mild.
Usually mild, factor V deficiency affects approximately 1 in 1 million.
Affecting about 1 in 500,000 people, factor VII deficiency can range from mild to severe depending on factor levels. Factor VII deficiency may be inherited or acquired due to liver disease, vitamin K, or the effects of blood thinner medications.
Approximately 1 in 1 million people have factor X deficiency, which can range from moderate to severe. Factor X deficiency is also known as Stuart-Prower deficiency.
Factor XI deficiency is also referred to as hemophilia C. About 1 in 100,000 people have factor XI factor deficiency, which usually ranges from mild to moderate.
When it occurs, factor XIII deficiency is severe. Luckily it is also extremely rare — about 1 in 3 million people have factor XIII deficiency.
Rarely, some people have deficiencies of more than one clotting factor. Deficiency in factors V and VIII may be the most common combination deficiency. In combined V and VIII deficiency, the body makes these two factors but is unable to transport the clotting factor into the blood.
Extremely rarely, some people are deficient in all clotting factors that are dependent on vitamin K, which include factors II, VII, IX, and X. This condition, known as vitamin K-dependent clotting factor deficiency, may be passed on in families or acquired as a result of liver failure, lack of vitamin K, or overdose of warfarin, a blood thinner medication. It is not known how many people might have vitamin K-dependent clotting factor deficiency.