Symptoms and Causes of Hemophilia A

Table of Contents
View All
Table of Contents

Hemophilia A is a bleeding disorder that can range in severity. Mild hemophilia A can cause slightly increased bleeding and bruises after an injury without dangerous consequences. But severe disease can cause extensive bleeding that could be life-threatening.

The most common type of hemophilia A is caused by a genetic defect that results in faulty production of clotting factor VIII. This is usually hereditary, but some people can have the mutation without inheriting it.

Others acquire hemophilia A later in life due to forming auto-antibodies against clotting factor VIII, often in association with an autoimmune disease, cancer, or pregnancy. This form is not hereditary.

This article will cover the symptoms and causes of hemophilia A.

Hemophilia A can cause excessive bleeding

kokouu / Getty Images

Frequent Symptoms 

The most common symptom of hemophilia A is bleeding after an injury. Sometimes bleeding can occur spontaneously, without any identifiable cause.

The symptoms of congenital hemophilia A, the hereditary form, can begin to become noticeable during infancy or childhood. The symptoms of acquired hemophilia A, which is not hereditary, usually begin after age 50.

Common effects of hemophilia A include:

  • Nose bleeds
  • Large amounts of menstrual bleeding in people who menstruate (hemophilia A does not affect the timing of the menstrual cycle) 
  • Bleeding gums or bleeding in your mouth
  • Bleeding for a long time after a cut or wound
  • Bruises after a bump
  • Blood in the stool 
  • Hematuria (blood in the urine)
  • Bleeding in the joints 

The amount of bleeding can vary. For example, you might be able to stop your bleeding after an injection by holding pressure over the puncture site for a few minutes, or you could soak several bandages over the course of hours. 

Some people with hemophilia A only have these symptoms when there is a cause. For example, you might have bleeding gums after a deep tooth cleaning, or nosebleeds when you blow your nose a lot due to a cold. But these symptoms can also occur without any reason. 


Bleeding from hemophilia A can affect the internal organs of your body, potentially leading to severe complications and organ damage. 

Bleeding may affect the:

  • Joints, causing hemarthrosis (tender, painful, swollen, and stiff joints, as well as joint damage)
  • Digestive system, causing bleeding in the stool 
  • Kidneys, causing blood in the urine and potentially kidney damage 
  • Brain, causing headaches, brain damage, and seizures
  • Lungs, causing hemoptysis (coughing blood) and difficulty breathing 

These issues can be life-threatening if the bleeding is severe, or if blood accumulates within an organ or in spaces of the body. 

Excess bleeding inside the body or from a wound can cause you to have a low amount of blood circulating throughout your body. This is harmful because the cells in your body need to have enough blood supply to survive. 

Blood loss can happen rapidly with an episode of excess bleeding, or it can happen gradually due to recurrent bleeding. 

When to See a Doctor/Go to the Hospital 

Often, the diagnosis of hemophilia A is made with a screening test if you have a family history of the condition. But the condition can develop without a hereditary pattern, and some people are diagnosed due to symptoms of excessive bleeding. 

If you already know that you have a family history of the condition, you should be tested for it. Some people who have severe cases of hemophilia A in the family may want to get tested before pregnancy for family planning purposes. 

If you or your partner becomes pregnant and has hemophilia A or a family history of the condition, you need to discuss this with your doctor. It’s important to have your baby tested.

If you know that you or your child has hemophilia A, you should get urgent medical attention if you experience signs of dangerous bleeding. 

Signs that you need prompt medical attention include: 

  • Severe headaches 
  • Blood clots or large amounts of blood in the stool or urine
  • Coughing blood 
  • Vomiting blood 
  • If you menstruate, clots of blood when you are not having your period or excessive bleeding during your period 
  • Difficulty breathing or swallowing 
  • Feeling lightheaded or dizzy 
  • Chest pain 
  • Sudden lump anywhere on your body 
  • Bleeding in your eye or vision changes 

Action Plan

You should discuss a plan of action with your doctor so that you and your family will know when to get medical attention and where you should go.


The body heals from wounds through a cascade of events that involves several proteins that help the blood clot. Hemophilia A is caused by a deficiency of factor VIII, an important protein in the cascade. When this protein, also described as a clotting factor, is deficient, blood clotting can be slow, and bleeding can occur.

There is often some amount of normal factor VIII with hemophilia A, and the other clotting factors involved in the cascade are usually normal. So, your body can form blood clots when you have hemophilia A, but the blood clotting is defective,

Some people may develop the condition due to antibodies against factor VIII—this is described as acquired hemophilia A. It is not hereditary and is often associated with underlying cancer, autoimmune disease, or pregnancy.


Hemophilia A is often caused by a genetic defect. The F8 gene, located on the X chromosome, codes for factor VIII. The defect can be hereditary from parent to child, or it can develop spontaneously, without a family history of the condition. 

The pattern of inheritance, described as X-linked, affects males and females differently because most females have two X chromosomes (XX), and most males have an X chromosome and a Y chromosome (XY):

  • XY males who have the gene that causes hemophilia A will develop clinical effects of the condition because they don’t have another X chromosome that correctly codes for factor VIII.
  • XX females who have the gene that causes hemophilia A on one X chromosome are likely to have a healthy version of the gene on their other X chromosome, so they will not have effects of the condition or might have mild effects. 
  • XX females who have the disease-causing gene on both of their X chromosomes will have the condition.

Lifestyle Risk Factors 

There are no lifestyle causes of hemophilia A, but your lifestyle can make you more likely to bleed. Engaging in contact sports or activities that lead to fall risks can increase the chances of excessive bleeding.

Sometimes, less intense injuries, such as from shaving without adequate moisturizer or picking at a hangnail, can cause bleeding. You will be able to notice the patterns of activities that make you more likely to bleed. 

Additionally, taking medication that can cause bleeding as a side effect, such as over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs), may increase your risk of bleeding. These medications cause bleeding in a different way than the bleeding of hemophilia A. 


Hemophilia A is a condition that makes people prone to bleeding. It can cause many types of mild, moderate, or severe bleeding throughout life. This can include bleeding gums, bruises, or internal bleeding.

Many people have mild or moderate forms of disease that can be controlled with treatment. In severe cases, organ damage or blood loss can occur. The bleeding occurs because of an insufficient amount of factor VIII.

If you have hemophilia A, you may have inherited it from one of your parents, and your kids can inherit it from you with an X-linked inheritance pattern. Sometimes the condition occurs without a family history. 

A Word From Verywell

Hemophilia A can cause many different bleeding symptoms, and sometimes mild injuries can cause the bleeding. It’s a good idea for you to be familiar with the effects of your condition so you can stop what you are doing to tend to your bleeding and so that you will know when to get medical attention.

If certain things make you more likely to bleed—such as getting your teeth cleaned or having your blood tested—be sure to plan ahead to give yourself time to recover and heal.

3 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Pai M. Acquired hemophilia A. Hematol Oncol Clin North Am. 2021;35(6):1131-1142. doi:10.1016/j.hoc.2021.07.007

  2. National Organization for Rare Disorders. Hemophilia A.

  3. Zwagemaker AF, Gouw SC, Jansen JJ, et al. Incidence and mortality rates of intracranial hemorrhage in hemophilia: a systematic review and meta-analysis. Blood. 2021 Aug 19:blood.2021011849. doi:10.1182/blood.2021011849

By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.