Hemophilia A

Hemophilia A is one of three types of hemophilia, a rare, inherited blood disorder. It happens when your blood doesn’t clot as it should, which is when bleeding stops or slows down. Hemophilia A usually affects men and people assigned male at birth (AMAB), but it may also affect women and people assigned female at birth (AFAB).


What is hemophilia A?

Hemophilia A (classic hemophilia) is one of three types of hemophilia. Hemophilia is a rare blood disorder that happens when your blood doesn’t clot as well as it should. People who have this condition don’t have enough of a certain blood protein (clotting factor) that helps make blood clot. Hemophilia A usually affects men and people assigned male at birth (AMAB), but can also affect women and people assigned female at birth (AFAB). Healthcare providers currently treat this condition by replacing the missing clotting factor. Healthcare providers are also researching gene therapy and gene replacement therapy as new ways of treating hemophilia A and other forms of hemophilia.


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How does hemophilia A affect my body?

People can be born with mild, moderate or severe forms of hemophilia A. People who have mild or moderate hemophilia A may have trouble controlling bleeding after being injured or having surgery. People who have severe hemophilia A may develop spontaneous bleeding into their joints that’s very painful and affects their ability to get around. Bleeding in other sites of your body is also possible.

Is hemophilia A common?

No, hemophilia A and all other types of hemophilia are rare disorders. Healthcare providers estimate about 12 in 100,000 people in the United States AMAB have hemophilia A.

What are other hemophilia types?

Hemophilia type B and type C are other hemophilia types. Like hemophilia A, types B and C happen when genetic mutations affect blood-clotting proteins that help slow or stop bleeding.

Is hemophilia A worse than hemophilia B?

Studies show hemophilia B may be less serious than hemophilia A. Hemophilia B is still a serious medical condition, but people who have this form of hemophilia may have fewer problems with excessive bleeding. Here are some other differences between hemophilia A and B:

  • Studies show people who have hemophilia B have fewer hemarthrosis, or bleeding into their joints, and less joint damage from that bleeding into their joints.
  • People with hemophilia B have fewer episodes of spontaneous bleeding, meaning bleeding that happens without apparent cause.
  • Sometimes, people treated for hemophilia develop problems with antibodies that interfere with treatment. Studies show people who have hemophilia B are less likely to develop these issues.

Symptoms and Causes

What causes hemophilia A?

Our bodies have 13 clotting factors, or proteins, that work together to form a blood clot. If you have hemophilia A, you’re missing factor VIII, a blood protein that helps your blood to form clots.

Normally, a gene called F8 carries instructions on how to create factor VIII. Hemophilia A happens when that gene mutates and becomes an abnormal gene that makes a faulty version of factor VIII or doesn’t make factor VIII at all. About 70% of people who have hemophilia A inherited the disorder. But 30% of people with hemophilia A develop the disorder spontaneously, meaning they don’t have a family history of hemophilia.

Men and people AMAB inherit hemophilia if their biological mothers carry the condition. Here’s how that happens:

  • The F8 gene sits on the X chromosome.
  • Women and people AFAB inherit two X chromosomes, one each from their mother and father.
  • Men and people AMAB inherit an X chromosome from their mother and a Y chromosome from their father.
  • If a woman or someone AFAB has an abnormal F8 gene on one of their X chromosomes, they carry hemophilia, but they won’t have symptoms. That’s because there’s a normal F8 gene on their second X chromosome.
  • They can pass the chromosome carrying the abnormal F8 gene on to their sons. Because men and people AMAB have just one X chromosome, their sons will develop hemophilia. Men and people AMAB can’t pass hemophilia on to their sons, though.
  • If a woman or someone AFAB has a daughter, they may also pass this chromosome on to that child. Because women and people AFAB have two X chromosomes, their baby is likely to inherit a healthy X chromosome from their father.
  • Women and people AFAB who inherit a healthy chromosome and a chromosome carrying the mutated F8 gene can pass the gene on to their children. These people are sometimes referred to as carriers.

Can women and people AFAB develop hemophilia, including hemophilia A?

They can, but symptomatic hemophilia in women and people AFAB is much less common than symptomatic hemophilia in men (AMAB). Some women and AFAB have hemophilia because both X chromosomes are affected, or one chromosome is affected and the other isn’t functioning enough. They may have the same hemophilia symptoms as men and people AMAB, but they’re more likely to have a mild form of hemophilia and less serious symptoms. That said, women and people AFAB who have hemophilia may have unusually heavy or prolonged periods (menstrual cycles), heavy bleeding after giving birth and other medical issues.


What are hemophilia A symptoms?

Hemophilia A symptoms vary depending on whether the condition is mild, moderate or severe. About half of all people with hemophilia A have a severe form of the condition.

Mild symptoms

People who have factor VIII levels of more than 5% up to 40% have mild hemophilia A and mild symptoms. In this case, people may not have any symptoms until they’re adults. Some people don’t notice symptoms unless they need surgery, are injured or have dental procedures. In those circumstances, the most common symptoms are bleeding more than expected after surgery, being injured or having dental treatment. People may also have bleeding that lasts longer than expected.

Moderate symptoms

People who have factor VIII levels between 1% and 5% have moderate hemophilia A and moderate symptoms. Moderate hemophilia A symptoms typically surface when children are toddlers. They may have the following symptoms:

  • Bruising: They bruise very easily.
  • Unusual bleeding: If they have surgery, have an injury that causes bleeding or have a tooth pulled, they’ll bleed more than normal and for a longer time than expected.
  • Spontaneous bleeding: Rarely, they’ll begin to bleed for no apparent reason.

Severe symptoms

People who have less than 1% of factor VIII in their blood have severe hemophilia A and severe symptoms. Many times, hemophilia A symptoms appear as children are being born or, in the case of male babies, when they’re being circumcised. Other times, children develop symptoms a few months after they’re born. Common symptoms include:

  • Bleeding:Babies and toddlers may bleed from their mouths after minor injuries, like bumping their mouths on a toy.
  • Swollen lumps on their heads: Babies and toddlers who bump their heads often develop goose eggs — large round lumps on their heads.
  • Fussiness, irritability or refusing to crawl or walk:These symptoms may happen if babies and toddlers have internal bleeding into a muscle or joint. They may have areas on their bodies that look bruised and swollen, feel warm to your touch or cause pain when you gently touch the area.
  • Hematomas:A hematoma is a mass of congealed blood that gathers under babies’ or toddlers’ skin. Babies and toddlers may develop hematomas after receiving an injection.
  • Breathing difficulties: Sometimes, bleeding may cause your child’s tongue to swell so much that it blocks their airway.

Diagnosis and Tests

How do healthcare providers diagnose hemophilia A?

Healthcare providers use blood tests to diagnose this condition. Those tests include:

  • Complete blood count: Healthcare providers use this test to measure and study blood cells.
  • Prothrombin time (PT) test: Healthcare providers use this test to see how quickly your blood clots.
  • Activated partial thromboplastin time test:This is another blood test to time blood clot formation.
  • Fibrinogen test:This is a blood test to measure the amount of blood protein fibrinogen, which helps with clotting.
  • Clotting factor test:This blood test shows the hemophilia type and severity.

Management and Treatment

How do healthcare providers treat hemophilia A?

Healthcare providers typically treat hemophilia A with factor replacement therapy. If you’re receiving this treatment, your healthcare providers will inject concentrated factor VIII into your bloodstream. Factor VIII replaces the missing blood protein, or factor, that helps blood to clot, so you’re less likely to have excessive bleeding and/or be able to control bleeding when it happens. Usually, people with mild or moderate hemophilia A don’t need replacement therapy unless they’re going to have surgery or if they’re dealing with a bleeding episode. Healthcare providers often treat people who have severe hemophilia A with regular factor replacement therapy. Another treatment option is a drug called emicizumab, which is a monoclonal antibody that substitutes the normal function of factor VIII.

What are replacement therapy complications?

People receiving replacement therapy may develop complications, including inhibitors and viral infections.


People develop inhibitors when their bodies stop accepting the factor treatment as part of their normal blood. Inhibitors prevent factor treatment from working, which may make it difficult to slow or stop bleeding episodes. About one-third to one-fifth of people who have severe hemophilia A may develop inhibitors. People are more likely to develop this complication if they have severe bleeding disorders and are receiving high doses of factor replacement therapy. Healthcare providers may treat this complication by using a higher dose of replacement therapy or different replacement therapy.

Viral infections

Rarely, people may develop viral infections, particularly hepatitis C, if they receive clotting factors from human blood. This is much less common with current Red Cross screening procedures.


Can type A hemophilia be prevented?

You can’t prevent hemophilia A because it’s an inherited condition.

I’m pregnant and carry hemophilia A. Can I find out if my baby has this condition before they’re born?

Yes, healthcare providers can take a sample of blood from your umbilical cord to test clotting factors. That way, you and they will know what to expect during delivery and take steps to prevent any complications bleeding may cause.

Outlook / Prognosis

What can I expect if I have this condition?

Most people receiving treatment have a good prognosis, or expected outcome. Studies show children who are treated for their hemophilia typically have a normal lifespan. People who have severe hemophilia A may develop other medical conditions that affect their overall health and lifespan. For example, bleeding into joints may lead to joint disease. If you have hemophilia A, ask your healthcare provider what you might expect. They know your situation, including your overall health, and are the best resource for information.

What can I expect if my child has this condition?

If your child has mild or moderate hemophilia A, make sure healthcare providers know about the condition. That way, they can take steps to prevent excessive bleeding if your child needs surgery or dental treatment like having a tooth pulled. Here are some other suggestions. Your healthcare provider may have more:

  • When your child is very little, you should make sure their high chairs and car seats have adequate safety straps.
  • As they grow up and play with other children, their caregivers and teachers should know what to do if your child is accidentally hurt and starts bleeding.
  • Your child may need to avoid certain activities, like sports where they’re likely to bump hard into other people or take hard falls.

My child has severe hemophilia A. What should I expect?

Children who have severe hemophilia A will need medical treatment for the rest of their lives, whether it’s treatment to prevent or slow bleeding or treatment to ease symptoms. Some potential challenges you may encounter, and some suggestions that may help, include:

  • Babies and toddlers with hemophilia A may start bleeding simply by bumping into things or falling as they learn to walk. You can’t always prevent those tumbles but it may make sense to put protective covering on any sharp edges on furniture.
  • As your child grows up and starts playing or running about, talk to your healthcare provider about protective gear like helmets and kneepads. Of course, all children should wear helmets when riding bikes. Your child may need extra protection to avoid bumps that could cause bleeding.
  • Your child will probably need regular medical treatment to prevent bleeding. They may get frustrated and angry if their appointments for treatment mean they can’t be with their friends or miss school or social activities.
  • A child who has hemophilia knows their teachers and other people are aware of their situation. They may feel awkward if teachers and other school staff try to be helpful by treating them differently.
  • All children want to fit it in. Having a rare disease like hemophilia A may make children feel self-conscious about their illness. Older children and teenagers may need help coping with their feelings and managing their reactions to other people. If that’s your child’s situation, talk to your healthcare provider about programs or support groups for young people.

Living With

Living with hemophilia A means being vigilant about treatment and taking extra steps to protect your overall health. Here are some suggestions:

  • Protect yourself from infection: Ask your healthcare provider what vaccinations make sense.
  • Aim for a healthy weight: Managing your weight may help if you’re having trouble getting around because internal bleeding damaged your joints.
  • Develop an exercise routine: You may worry about hurting yourself during exercise. Talk to your healthcare provider about ways to reduce the risk of bleeding while staying active.
  • Manage your stress: Hemophilia A is a lifelong illness. It may take extra effort to balance your obligations to your family and your work.
  • Avoid certain pain medications: If you have hemophilia A, you shouldn’t take aspirin or ibuprofen. These pain medications interfere with blood clotting.

When should I see my healthcare provider?

You should see your healthcare provider for your regular treatment and any time you have unusual bleeding or other symptoms like severe joint pain.

When should I go to the emergency room?

You should seek immediate medical help if you have a head injury. The following symptoms could mean you have brain bleed or hemorrhage (intracranial hemorrhage):

Contact your healthcare provider or go to the emergency room any time you can’t stop bleeding from any kind of injury or if you start to bleed for no apparent reason.

A note from Cleveland Clinic

Hemophilia A is a rare, inherited blood disorder that may cause a range of symptoms, complications and challenges. Living with hemophilia may mean taking additional steps to prevent and manage bleeding. For example, you may need to avoid certain activities or take additional precautions when you have surgery or see your dentist. If you’re raising a child who has hemophilia A, you’ll need to help them adjust to living with a condition that affects their lifestyle. Women and people AFAB who carry the condition may wonder and worry if they’ll pass it on to their children. For some people, having hemophilia A means a lifetime of medical treatment to prevent excessive bleeding. Researchers are investigating new treatments like gene replacement or gene therapy that may make a huge difference in how healthcare providers treat severe hemophilia A. If you or your child has this condition, ask your healthcare provider if there are clinical trials that may be appropriate, given your situation.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 06/03/2022.

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