Hemophilia A
Hemophilia A

About hemophilia A – factor VIII deficiency

Hemophilia A, also called classic hemophilia, is the most common type of hemophilia. It occurs when clotting factor VIII is either absent or not present in sufficient amounts. Primarily affecting males, hemophilia A happens in 1 in 5,000 live male births.1

From mild to severe hemophilia A

The severity of hemophilia A is related to the amount of clotting factor that is either missing or deficient.2

The severity of hemophilia A is related to the amount of clotting factor that is either missing or deficient.

Approximately 60% of hemophilia A patients have the severe form of the disorder. They may experience bleeding following an injury or frequent spontaneous bleeding episodes (bleeds that occur without an obvious cause) typically into their joints and muscles.2

When considering the levels of severity, keep in mind that individual bleeding patterns vary. For example, some people with moderate hemophilia can bleed just as much as those with severe hemophilia.3

Diagnosing hemophilia A

If hemophilia A is suspected, specific blood tests are used to measure how long it takes blood clots to form. If blood clot formation is not within the normal range, then a clotting factor activity test is performed to confirm the diagnosis of hemophilia A, or another blood clotting factor deficiency.1

“When I was finally diagnosed, I felt hopeful. I knew there was support out there for me.” — Cathy, hemophilia A patient

Once the diagnosis of hemophilia A is made, genetic testing can help predict a patient’s risk of developing inhibitors to factor treatment. Analysis of the specific gene mutation can also help identify female carriers of hemophilia A in a given family. Genetic information like this can aid in the diagnosis of hemophilia A prior to birth and after delivery.1

How hemophilia A is inherited

Hemophilia A is often an inherited bleeding disorder and is most common in male patients. However, in about 30% of hemophilia A cases, there is no family history of the disorder and it is the result of a spontaneous gene mutation.1

Hemophilia is the result of an inherited genetic mutation.

The diagram above shows how the mutated gene found on the X chromosome is inherited. Because hemophilia is an X-linked recessive disorder, it can only be passed from a mother to her child via the X chromosome. A female who has one of the affected gene mutations is known as a 'carrier.'4

This diagram shows the inheritance pattern of a mother who is a carrier and a father who does not have hemophilia.2 Each pregnancy has a 25% chance of resulting in a male with hemophilia, a 25% chance of resulting in an unaffected male, a 25% chance of an unaffected female, and a 25% chance of a female carrier.1,4

In rare instances, females may also develop hemophilia if both of their X chromosomes have the mutation or one is affected and the other is missing or inactive.4

Acquired hemophilia A

While most people with hemophilia A are born with it, some people do develop it later in life. When this happens, it is called acquired hemophilia A. In this case, the body produces antibodies that prevent clotting factors in the blood from working. These antibodies attack clotting factor VIII.5 Affected individuals often don’t know they have a bleeding disorder until they develop complications associated with abnormal, uncontrolled bleeding into the muscles, skin, and soft tissue during surgery or following trauma.1

Treatment for hemophilia A

Options are available for this factor VIII deficiency.

Learn more

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  1. Hemophilia A. National Organization for Rare Disorders website. https://rarediseases.org/rare-diseases/hemophilia-a/. Accessed August 20, 2019.
  2. Hemophilia A. National Hemophilia Foundation website. https://www.hemophilia.org/Bleeding-Disorders/Types-of-Bleeding-Disorders/Hemophilia-A. Accessed August 20, 2019.
  3. Severity levels. The Hemophilia, von Willebrand Disease & Platelet Disorders Handbook website. https://www.hog.org/handbook/article/1/3/severity-levels. Accessed August 26, 2019.
  4. What is hemophilia? Centers for Disease Control and Prevention website. http://www.cdc.gov/ncbddd/hemophilia/facts.html. Reviewed September 6, 2018. Accessed August 20, 2019.
  5. Paul Giangrande; World Federation of Hemophilia. Acquired hemophilia. http://www1.wfh.org/publication/files/pdf-1186.pdf. Published 2005. Revised 2012. Accessed August 20, 2019.

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