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Genetic Testing for Hemophilia A Explained

Updated on October 18, 2022
Medically reviewed by
Todd Gersten, M.D.
Article written by
Emily Wagner, M.S.

Hemophilia A is a rare bleeding disorder where the blood doesn’t clot easily. It occurs when a person has low coagulation or clotting factor levels in their blood. Hemophilia A causes mild to severe bleeding symptoms, large bruises, and painful or swollen joints. Hemophilia A is often passed down through family members due to changes in their DNA.

After a person receives a hemophilia A diagnosis, they may choose to have genetic testing done. Genetic testing looks for specific changes in DNA, known as mutations, that affect a person’s ability to make clotting factors. Some families may choose to have testing, while others may not.

What Is Genetic Testing?

Genetic testing is a method used to look for changes in a person’s DNA. These changes may cause certain diseases, such as hemophilia. Genetic testing uses DNA taken from a blood sample to look for specific gene changes. Genes provide instructions for making proteins. Sometimes, changes in genes (known as mutations) make them dysfunctional, and the genes cannot properly make proteins. As a result, diseases and other health conditions can develop.

A person may want to have genetic testing done for themselves or a loved one for several reasons. Genetic testing can confirm a diagnosis or rule out other health conditions. Genetic testing for hemophilia can also diagnose hemophilia in fetuses while still in the womb. This helps parents prepare for having a child with hemophilia.

Genetic testing can also help identify if a person “carries” a change in their DNA but doesn’t have the disease themselves. These people are known as carriers. Only females can be a carrier of a gene mutation for hemophilia A. This means they carry one healthy copy of a gene and one mutated copy. Generally, the healthy copy is able to compensate enough so that the person has few — if any — hemophilia A symptoms.

What Is Genetic Testing for Hemophilia A?

Genetic testing is mainly performed to confirm the type of mutation a person has after being diagnosed with hemophilia. Typically, these tests confirm the results of blood tests that show low levels of clotting factors. Carrier testing can also be done on family members to see if they also have a mutated gene.

How Is Hemophilia Inherited?

Hemophilia is a genetic disorder that is passed down through family members. The genes involved in hemophilia are found on the X chromosome. It is a recessive X-linked disorder. This means that only one mutated gene copy is necessary for the disease to occur.

Females have two X chromosomes, while males have an X and a Y chromosome. This means that females inherit one X chromosome from each parent. Males inherit one X chromosome from their mother and the Y chromosome from their father. This makes males more likely to develop hemophilia than females. It is much less common in females, but it can still occur.

A mother who has a gene mutation for hemophilia on one of her X chromosomes may pass it along to her children. A daughter is less likely to develop hemophilia; even if she receives the mutation from her mother on one X chromosome, the other X chromosome from her father can compensate with a healthy gene. On the other hand, a son who receives the X chromosome containing the mutation will develop hemophilia because the Y chromosome can’t compensate for it.

Gene Mutations in Hemophilia

The two genes involved in hemophilia are the F8 gene and the F9 gene. The F8 gene encodes instructions for making factor 8. It is responsible for causing hemophilia A. The F9 gene provides instructions for making factor 9. It is responsible for causing hemophilia B.

There are two main genetic mutations that can occur in the F8 gene. They are found in portions of DNA known as introns. Introns are numbered based on their location in the DNA sequence. People with hemophilia A can have an intron 1 or intron 22 inversion, meaning that these pieces of DNA are flipped. This affects the production of factor 8, which leads to hemophilia A symptoms.

Unlike hemophilia A, hemophilia B can be caused by one of more than 3,000 mutations in the F9 gene. These include:

  • Duplications — The same pieces of DNA are repeated.
  • Insertions — Extra pieces of DNA are added.
  • Deletions — Some pieces of DNA are missing.

Genetic Testing for Hemophilia

Genetic testing for hemophilia is done to confirm diagnosis and the type of mutation. In cases where there is a family history of hemophilia, certain tests can be done to confirm the mutation. For example, an intron 22 inversion test is performed only for those with another family member with the same mutation.

In cases of suspected hemophilia with no known family history, next-generation sequencing is used to look at the F8 or F9 genes for any mutations. This test can also be used to identify female carriers of hemophilia.

Benefits of Genetic Testing for Hemophilia

Genetic testing gives information on mutations in a person’s DNA. It can also be used to predict someone’s response to treatment. During or after hemophilia treatment with coagulation factor concentrates, some people develop antibodies known as inhibitors. These antibodies attack and destroy the clotting factors, making them ineffective. Genetic testing may offer doctors some insight into who may develop inhibitors, which can help them select the best treatment plan.

Genetic testing can also help relatives determine if they have hemophilia or are carriers of the disease. Knowing whether you are a carrier can help you make the best decisions for yourself and your family. If you are considering having children, knowing your carrier status can help with family planning. Some carriers may also have symptoms of mild hemophilia. Testing can help them get any necessary treatment.

Is Genetic Testing Right for You?

When deciding on genetic testing, it’s important that you take yourself and your family’s needs into consideration. Many people find knowing the results beneficial, but others may find the test results stressful.

If you need help understanding or processing a diagnosis, your doctor may provide a referral to a genetic counselor. Genetic counseling can help you and your family better understand your hemophilia diagnosis and how it impacts your lives. They can also provide resources and support for emotional and financial concerns.

How Much Does Genetic Testing for Hemophilia A Cost?

In general, genetic testing is covered by insurance as long as it’s ordered by a health care provider. It’s best to call your insurance company before undergoing testing to confirm that it’s covered by your plan.

If genetic testing isn’t covered by insurance, you may pay out-of-pocket costs. There are no set prices, as the cost typically depends on the type of testing being done. For example, the University of Pennsylvania charges between $360 and $1,350 for hemophilia testing, depending on the genes being tested.

Talk To Your Doctor About Genetic Testing for Hemophilia A

To learn more about genetic testing and whether it’s right for you and your family, talk to your doctor. They may refer you to a hemophilia treatment center for testing and treatment. Ultimately, the decision to be tested is up to you and your family. Be sure to consider the pros and cons of testing, including costs, how the results may affect your treatment plans, and the benefits of knowing the results.

Find Your Team

On MyHemophiliaTeam, more than 6,000 people living with hemophilia come together to ask questions, give advice, and share their stories with others who understand life with the condition.

Have you or a loved one had genetic testing for hemophilia? What was your experience? Share your hemophilia journey in the comments below, or start a conversation by posting on your Activities page.

References
  1. Hemophilia — Mayo Clinic
  2. Genetic Testing — MedlinePlus
  3. What Are the Uses of Genetic Testing? — MedlinePlus
  4. Information on Hemophilia for Women — Centers for Disease Control and Prevention
  5. Genetic Testing: What It Can Provide for You and Your Family — Indiana Hemophilia & Thrombosis Center
  6. Hemophilia — MedlinePlus
  7. Recessive Traits and Alleles — National Human Genome Research Institute
  8. Hemophilia Characteristics Among Women and Girls Receiving Care in Specialized Treatment Centers in the United States — Centers for Disease Control and Prevention
  9. F8 Gene — MedlinePlus
  10. F9 Gene — MedlinePlus
  11. Identification of the Intron 22 and Intron 1 Inversions of the Factor VIII Gene in Iraqi Kurdish Patients With Hemophilia A — Clinical and Applied Thrombosis/Hemostasis
  12. Mutation Analysis and Characterisation of the F9 Gene in Haemophilia-B Population of India — Blood Research
  13. Test ID: F822B — Mayo Clinic Laboratories
  14. Test ID: F8NGS — Mayo Clinic Laboratories
  15. What Is an Inhibitor? — National Hemophilia Foundation
  16. The Importance of Genetic Testing for Hemophilia — Children’s Hospital of Philadelphia
  17. What Are the Risks and Limitations of Genetic Testing? — MedlinePlus
  18. Genetic Counseling — Centers for Disease Control and Prevention
  19. Will Health Insurance Cover the Costs of Genetic Testing? — MedlinePlus
  20. What Is the Cost of Genetic Testing, and How Long Does It Take To Get the Results? — MedlinePlus
  21. Hemophilia A and B — Perelman School of Medicine at the University of Pennsylvania
    All updates must be accompanied by text or a picture.
    Todd Gersten, M.D. is a hematologist-oncologist at the Florida Cancer Specialists & Research Institute in Wellington, Florida. Review provided by VeriMed Healthcare Network. Learn more about him here.
    Emily Wagner, M.S. holds a Master of Science in biomedical sciences with a focus in pharmacology. She is passionate about immunology, cancer biology, and molecular biology. Learn more about her here.

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