Hemophilia (say: hee-muh-fih-lee-uh) is a genetic disorder in which a person's blood does not clot properly.

A person who has hemophilia has a tendency to bleed excessively. Think of the last time you had a cut or scrape. When the bleeding stops on its own, you're seeing clotting in action.

A Bit About Blood

If your blood is clotting normally, your body naturally protects itself. Platelets, which are "sticky cells," go to where the bleeding occurs and cover the hole, plugging it up. This is the first step in the clotting process. When the platelets plug the hole, they release chemicals that attract more sticky platelets and also activate various clotting factors, which are proteins in the blood.

These proteins mix with the platelets to form fibers, which make the clot stronger and stop the bleeding. Our bodies have clotting factors that work together to make fibrinogen (say: fy-brih-nuh-jun), the substance that makes the fibers. Trouble begins if the body is missing one of these factors.

A person can have one of two types of hemophilia, A or B. It depends on which clotting factor they are low on. If someone produces 1% or less of the affected factor, the case of hemophilia is called severe. Someone who produces 2% to 5% has a moderate case, and someone who produces 6% to 50% of the affected factor level is considered to have a mild case of hemophilia.

Why Do Kids Get Hemophilia?

Hemophilia almost always affects boys. Why? Because the disease is an X-linked genetic disorder, passed from mother to son. Boys get an X chromosome (say: kro-muh-soam) from their mother and a Y chromosome from their father. If the mother carries the gene for hemophilia on one of her X chromosomes (girls have two X chromosomes), each of her sons will have a 50% chance of having hemophilia.

A mother who is a carrier also has a 50% chance of giving the faulty X chromosome to her daughter. That does not give the daughter the hemophilia disease, but it does result in the daughter becoming a hemophilia carrier. So it's possible one of her sons someday could have the disease.

How Do Doctors Know a Kid Has Hemophilia?

Doctors may find out that a baby has hemophilia if he bruises easily or bleeds a lot after getting a cut. Another sign is swelling in a baby's joints. Babies who are learning to crawl usually bump into things, but ordinarily this doesn't cause swelling in their joints. If they do, it's a tip-off that there may be bleeding in the joints, which usually doesn't happen from normal activities or minor bumps.

Doctors will ask parents questions and do some blood tests to figure out whether the baby might have hemophilia. There is also a blood test that can be done to determine if the mother is a carrier.

What Do Doctors Do?

Even kids with severe hemophilia often live long and healthy lives. A cut or minor wound is usually no big deal for a person with hemophilia, but internal bleeding can be serious. When bleeding occurs in the joints, muscles, or internal body organs, treatment is necessary.

Patients with more serious cases of hemophilia often get regular shots of the factor that they're missing to prevent bleeding episodes. Kids with moderate or mild cases of hemophilia usually don't need these shots unless they have a more serious injury or require surgery.

Scientists are working to develop gene therapy for people with hemophilia. Gene therapy is an experimental technique that tries to provide the body with the genetic information it doesn't have. Hemophilia is considered a good test for gene therapy because it is caused by only one defective gene. It could be a way to change the way someone's body works so that the body can produce the missing clotting factors on its own.

How Kids With Hemophilia Can Stay Healthy

Life for a kid with hemophilia is much like life for any other kid. However, these kids need to take a few precautions. For instance, a kid with hemophilia who doesn't feel well should not take any product that contains aspirin, ibuprofen, or naproxen sodium. These medications make people without hemophilia bleed for a longer time, so they are a bad idea for anyone with the disease.

Heavy contact sports like wrestling, football, and hockey can be dangerous and are generally not safe for kids with hemophilia. Team sports, such as soccer, basketball, or baseball, present a risk for kids with hemophilia but are not off-limits.

But sports are encouraged for kids with hemophilia because exercise makes muscles stronger, which protects the joints. Weak muscles don't support the joints as well, making bleeding episodes more frequent.

Kids and their parents should talk with the doctor about choosing a sport, but swimming, running, and bicycling are often recommended. So if you have a friend who has hemophilia, maybe the two of you can get out there for some splashing, dashing, and biking!

Reviewed by: Steven Dowshen, MD
Date reviewed: January 2011