What is hemophilia?
Hemophilia is a rare, inherited bleeding disorder in which blood cannot clot normally at the site of a wound or injury. The disorder occurs because certain blood clotting factors are missing or do not work properly. Because a clot does not form, extensive bleeding can be caused from a cut or wound. This is called external bleeding. Bleeding inside the body, called internal bleeding, can occur as well, especially in muscles and in joints like the hips and knees.
Hemophilia affects males almost exclusively, but there are rare circumstances when a female can be affected with the disorder.
There are two main types of inherited hemophilia:
- Type A, the most common type, is caused by a deficiency of factor VIII, one of the proteins that helps blood to form clots. This type is known as classic hemophilia.
- Type B hemophilia is caused by a deficiency of factor IX. This type is also called Christmas disease.
Although hemophilia is usually diagnosed at birth, the disorder can also be acquired later in life if the body begins to produce antibodies that attack and destroy clotting factors. However, this acquired type of hemophilia is very rare. Acquired hemophilia is also called autoimmune hemophilia, or acquired hemophilia A (AHA).
How common is hemophilia?
Hemophilia is a rare disorder. It can occur in all races and ethnic groups. Hemophilia A affects 1 in 5,000 to 10,000 males. Hemophilia B is less common, affecting 1 in 25,000 to 30,000 males.
Around 60% to 70% of people with hemophilia A have the severe form of the disorder and about 15% have the moderate form. The rest have mild hemophilia.
Is hemophilia contagious?
No. Hemophilia is caused by mutations in the genes encoding factor VIII and IX. You can’t catch it from someone who has it like you can catch a cold.
What causes hemophilia?
The genes that regulate the production of factors VIII and IX are found on the X chromosome only. Hemophilia is caused by mutations in either the factor VIII or factor IX genes on the X chromosome.
If a woman carries the abnormal gene on one of her X chromosomes (females have a pair of X chromosomes), she will not have hemophilia herself, but she will be a carrier of the disorder. That means that she can pass the gene for hemophilia on to her children. There is a 50% chance that any of her sons will inherit the gene and will be born with hemophilia. There is also a 50% chance that any of her daughters will be carriers of the gene without having hemophilia themselves.
It is very rare for a girl to be born with hemophilia, but it can happen if the father has hemophilia and the mother carries the gene for hemophilia. The daughter will then have the abnormal gene on both of her X chromosomes.
In about 20% of all cases of hemophilia, the disorder is caused by a spontaneous gene mutation. In such cases there is no family history of abnormal bleeding.
What are the symptoms of hemophilia?
The major symptom is bleeding, either prolonged external bleeding or bruising after minor trauma or for no apparent reason. Symptoms vary depending on whether the patient has the mild, moderate, or severe form of the disorder:
- In severe hemophilia, unprovoked (spontaneous) bleeding episodes occur often.
- In moderate hemophilia, prolonged bleeding tends to occur after a more significant injury.
- In mild hemophilia, a patient might have unusual bleeding, but only after a major injury, surgery, or trauma.
People with hemophilia may have any type of internal bleeding, but most often it occurs in the muscles and joints, such as the elbows, knees, hips, shoulders and ankles. There may be no pain at first, but if the bleeding continues, the joint may become hot to the touch, swollen, and painful to move.
Repeated bleeding into the joints and muscles over time may cause permanent damage, such as joint deformity and reduced mobility.
Bleeding in the brain is a very serious problem for those with severe hemophilia. It may be life-threatening. Get medical help immediately if you have signs of bleeding, such as:
- Changes in behavior.
- Excessive sleepiness.
- Headache that will not go away.
- Neck pain.
- Double vision.
- Convulsions or seizures.