What are the causes of hemophilia?

Hemophilia (heem-a-FILL-ee-ah) is a rare inherited bleeding disorder in which the blood does not clot normally. Persons with hemophilia may bleed for a longer time than others after an injury or accident. They also may bleed internally, especially in the joints (knees, ankles, and elbows).

Babies born with hemophilia are missing or have a low level of a protein needed for normal blood clotting or blood coagulation (coe-AG-you-lay-shun). The protein is called a clotting factor.

About 18,000 people in the United States have hemophilia. Each year, about 400 babies are born with the disorder. Hemophilia usually occurs only in males (with very rare exceptions).

A person with hemophilia has a problem with certain proteins in the blood called clotting factors. Hemophilia can be due to:

A low level of one of the clotting factors
A clotting factor that is completely missing
When clotting factors are missing, or your body does not have enough of these factors, it can take a long time for your blood to clot after an injury or accident.

What Is Clotting?

An injury (like a cut) to a blood vessel causes a complex chain of events that results in a blood clot. This clotting process is also called blood coagulation. Clotting is your body鈥檚 reaction to bleeding and keeps you from losing too much blood. Losing too much blood can be life threatening and can damage your internal organs.

What Is a Clotting Factor?

Clotting factors are proteins in the blood that work with platelets鈥攁 type of small blood cell鈥攖o help the blood to clot. When blood vessels are damaged, clotting factors help the platelets stick together to plug cuts and breaks at the site of the injury.

In people with hemophilia, blood does not clot as it should because it is missing or has low levels of one of these clotting factors. If blood doesn鈥檛 clot as quickly or as well as it should, then:

Heavy blood loss can occur.
Body organs and tissues can be injured.
These conditions can result in permanent damage or death.
Sometimes people with hemophilia need infusions of a clotting factor or factors to stop bleeding.

Types of Hemophilia

The two main types of hemophilia are:

Hemophilia A: Clotting factor VIII (8) is low or missing. About 9 of 10 people with hemophilia have type A.
Hemophilia B: Clotting factor IX (9) is low or missing.
Hemophilia also can be acquired when antibodies to these clotting factors form and block their function. Only inherited hemophilia is discussed here.

Hemophilia can be:

Mild
Moderate
Severe
Mild, moderate, or severe hemophilia is determined by the amount of clotting factor in the blood. About 7 of 10 people with hemophilia A have the severe form. Normal persons have a factor VIII activity of 100 percent; persons with severe hemophilia A have a factor VIII activity of less than 1 percent.

A genetic mutation in the gene that codes for red blood cells.

Hemophilia is a genetic disorder - many times caused by inbreeding - see the Romanoffs- where a defective gen causes the absence of one of the 16 enzymes needed for blood to clot after a trauma. Appears only in males and as females are asymptomatic carriers it jumps one generation.