What is hemophilia?

Hemophilia is a rare genetic bleeding disorder that almost always occurs in males. A person has hemophilia when he or she inherits problems with certain blood-clotting factors, making them unable to work properly. Blood-clotting factors are needed to help stop bleeding after a cut or injury and to prevent spontaneous bleeding. The hemophilia gene can contain many different errors, leading to different degrees of abnormality in the amount of clotting factor produced.

There are two major types of hemophilia:

• Hemophilia A is caused by a deficiency of active clotting factor VIII (8). Approximately 1 out of every 5,000 male babies is born with hemophilia A.¹
• Hemophilia B (Christmas disease) is caused by a lack of active clotting factor IX (9). It is less common, occurring in 1 out of every 30,000 male babies.¹

Hemophilia is usually classified by how severe it is. There are three levels of hemophilia, although they can overlap. The severity of the disease is defined by how much clotting factor is produced and in what situations bleeding most often occurs.

• Mild hemophilia: Clotting factor VIII or clotting factor IX level is 5% of normal or greater. Mild hemophilia might not be recognized unless there is excessive bleeding after a major injury or surgery.
• Moderate hemophilia: Clotting factor VIII or clotting factor IX level is 1% to 5% of normal. Bleeding usually follows a fall, sprain, or strain.
• Severe hemophilia: Clotting factor VIII or clotting factor IX level is less than 1% of normal. Bleeding often happens one or more times a week for no apparent reason (spontaneously).

The percentage of clotting factors stays about the same throughout a person's life. All family members who have hemophilia usually will have similar types.

In very rare cases, a person develops a type of hemophilia, called acquired hemophilia, that is not inherited. If you have acquired hemophilia, your clotting factors don't work properly because your body makes antibodies that attack them.

What causes hemophilia?

Hemophilia A and hemophilia B are caused by an inherited defect in a pair of chromosomes. The defect affects how much clotting factor a person will produce and how the factor will function. Hemophilia is mild when the clotting factor functions are close to normal and the amount of clotting factor is almost normal. The less normal the function and amount of clotting factor, the more severe the hemophilia.

What are the symptoms?

Symptoms of hemophilia are usually first noticed during infancy or childhood. But some people who have milder forms of hemophilia may not develop symptoms until later in life.

The following are signs of hemophilia that may be noticed shortly after birth:

• Bleeding into the muscle, resulting in a deep bruise after receiving a routine vitamin K shot
• Prolonged bleeding after a boy is circumcised
• In rare cases, prolonged bleeding after the umbilical cord is cut at birth