Hemophilia is a rare genetic bleeding disorder in which a person 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. People who have hemophilia are at risk of abnormal bleeding throughout the body, especially in the joints and muscles, which may lead to disabling joint problems.

Hemophilia occurs almost exclusively in men. The disease can be passed from a mother who is a carrier of the genetic defect (but who does not have the disease) to her son. Rarely, a girl can have hemophilia. This occurs only if she inherits a defective gene from both her mother and her father.

Symptoms of hemophilia are usually first noticed during infancy or childhood. However, 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

Other symptoms of hemophilia include easy bruising, frequent nosebleeds, blood in the urine, and bleeding after dental work.

Some people who have hemophilia may need to inject (infuse) themselves with clotting factors to prevent uncontrolled bleeding. They may need to do this either regularly or only before activities or situations (such as surgery) when injury or bleeding may occur.