Hemophilia A overview

Last updated Oct. 31, 2025, by Susie Strachan
Fact-checked by Joana Carvalho, PhD

Hemophilia A is a rare genetic disorder that affects the blood’s ability to clot properly. It is the most common form of hemophilia, responsible for 80% of all cases.

The condition is caused by a mutation of the F8 gene on the X chromosome that leads to a deficiency of a protein called factor VIII (FVIII). This deficiency delays blood clotting after an injury, leading to prolonged bleeding.

While there currently is no way to cure hemophilia A, early diagnosis and regular factor replacement therapy can help prevent severe bleeding and long-term joint damage.

Hemophilia A genetics and inheritance

Hemophilia A inheritance follows an X-linked recessive pattern, which is why the prevalence of this disease type is higher in males. Estimates indicate that the disease affects 1 in every 5,000 male births.

Because they only have one X chromosome, if a male inherits an X chromosome with a faulty F8 gene, he will have hemophilia A.

Females, however, have two X chromosomes. If a female inherits one X chromosome with a faulty F8 gene and one with a healthy F8 gene, she is considered a carrier. Carriers may not have hemophilia A symptoms, but can still pass along to their children the F8 gene that causes the disease.

While hemophilia A is often passed down from parent to child, it also may result from a spontaneous mutation in the gene, which occurs in about one-third of cases.

Hemophilia A versus von Willebrand disease

Hemophilia A and von Willebrand disease, known for short as VWD, are bleeding disorders with different causes and characteristics.

VWD affects men and women equally, and is due to a deficiency or dysfunction of another clotting protein called von Willebrand factor. This protein helps platelets stick together and stabilizes factor VIII in the bloodstream. Although both diseases are marked by abnormal bleeding, symptoms tend to be milder in VWD.

Symptoms of hemophilia A

The main symptom of hemophilia A is bleeding that happens extremely easily and lasts an unusually long time. Some people have mild bleeding, while others have more severe and frequent bleeding episodes.

For newborns and infants, this may look like:

spontaneous intracranial bleeding, which is sudden bleeding within the brain or surrounding membranes
prolonged bleeding from the stump of the umbilical cord
excessive bleeding after circumcision, if that procedure is done
bleeding after vaccinations or injections
unexplained bruising

Intracranial bleeding occurs without any apparent trauma or injury to the head. Prolonged bleeding from an umbilical cord stump is a possible early sign of hemophilia A.

For adolescents and adults, symptoms may include:

prolonged bleeding, even with minor injuries, or bleeding from cuts that may be difficult to stop
being easily bruised, with bruises possibly being larger and more severe than normal
joint pain and swelling as a result of repeated bleeding into the joints, also known as hemarthrosis, which may affect the knees, elbows, and ankles
excessive bleeding during surgery or dental procedures
internal bleeding, affecting areas such as the mouth and muscles

Bleeding into the joints can erode joint cartilage if not properly manage. Internal bleeding is an indicators of severe hemophilia A.

Hemophilia A treatment

While there is no cure for hemophilia A, treatments are available to help manage your symptoms, improve life expectancy, and reduce the risk of complications. Treatment can support a favorable prognosis for people with hemophilia A.

In the past, people with hemophilia A could be at risk of contracting viral infections from contaminated clotting factor products. However, modern treatments use advanced purification methods and recombinant or lab-made versions of factor VIII, significantly reducing this risk.

Different hemophilia A management options include:

factor replacement therapy
nonfactor therapies
other clot-promoting medications
bypassing agents
gene therapy

Ultimately, the right approach to hemophilia A treatment depends on the severity of your condition, your bleeding symptoms, and your lifestyle.

Factor replacement therapy

The cornerstone of hemophilia A treatment involves administering a working form of the missing or faulty clotting protein to restore blood clotting.

This treatment may be used prophylactically to prevent bleeding episodes or on an on-demand basis to stop bleeding once it occurs.

Nonfactor therapies

Other medications that promote blood clotting through mechanisms that don’t involve replacing the missing or defective clotting protein may also be used to prevent or reduce the frequency of bleeds in people with hemophilia A.

Other clot-promoting medications

Medications such as antifibrinolytics, which promote blood clotting by preventing clot breakdown, may be used for mild to moderate cases.

Some people with mild hemophilia A may also benefit from DDAVP (desmopressin acetate), a medication that stimulates the release of stored factor VIII from within the body.

Bypassing agents

For people with inhibitors — neutralizing antibodies against factor VIII — bypassing agents may help manage bleeding.

They help blood clot without relying on the missing or blocked clotting factors, making them a useful alternative for people who have developed inhibitors to conventional factor replacement treatments.

Gene therapy

Gene therapy can deliver a healthy version of the defective gene, and restore the body’s ability to produce functional clotting proteins.

Hemophilia A diagnosis

A hemophilia A diagnosis is made through medical evaluations and tests.

You will be asked questions about your medical history, including whether you have a family history of bleeding disorders. Your healthcare provider will also ask about your symptoms, such as spontaneous bleeding, unusual bruising, and bleeding after injuries or surgeries.

Your clinician will then order blood tests such as partial thromboplastin time (PTT) and prothrombin time (PT), which can help assess your clotting function. A clotting factor test can confirm the diagnosis and determine the degree of disease severity by measuring the levels and activity of clotting factor VIII.

Hemophilia A is often diagnosed in the first few months of life, and about two-thirds of cases are confirmed shortly after birth. However, some people with milder hemophilia A may not be diagnosed until adulthood.

Living with hemophilia A

Living with hemophilia A is manageable with the right medical care and lifestyle choices, including:

learning about hemophilia A, its treatment, and potential complications, as this can help you make informed decisions
receiving regular care from a hematologist or hemophilia treatment center to monitor the disease and prevent complications
receiving factor replacement therapy or other prophylactic treatments as needed for the prevention of bleeding episodes
minimizing risks, such as using protective gear during physical activities and avoiding contact sports that could lead to injury
managing pain during bleeding episodes and from joint damage, which can include medications and physical therapy
staying physically active, eating a balanced diet, and maintaining a healthy weight to help keep joints and muscles strong
boosting mental health by talking with family and friends, joining support groups, and talking to a therapist
having a plan in case of a bleeding emergency and knowing how to administer treatment.

Hemophilia News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.