What is Hemophilia?
Find the answer to this question and ask more at Health Answers by Pfizer.
![]()
Typically inherited from one or both parents, hemophilia is a rare blood disorder that stops blood from clotting properly. Because people with hemophilia don’t have enough blood-clotting proteins or clotting factors, they may take longer to stop bleeding after surgery or an injury.1
For people living with hemophilia, bleeding can occur spontaneously or from an injury. Internal bleeding is a significant concern, as it can lead to organ damage or death.1,2
Worldwide, more than 200,000 people live with some form of hemophilia.3 New data, however, indicate that hemophilia might be underdiagnosed. The actual global population with hemophilia could be more than 1.1 million.4 The extent of hemophilia in the United States is unknown, but data suggests that about 33,000 people assigned male at birth are living with hemophilia nationwide.5
The condition most commonly affects those who were assigned male at birth.1 In one study, those assigned female at birth accounted for roughly 18% of mild hemophilia cases and less than 1% of severe cases.6 Hemophilia typically affects white and Hispanic patients, while it is less prevalent among Black and Asian patients.7
Hemophilia is often inherited, meaning genetics play a strong role in who develops hemophilia. But in some cases, hemophilia is acquired.2
In most cases, a mutation in the genes responsible for making clotting factors causes hemophilia.2 The genes for factors VIII and IX are only found on the X chromosome, while the factor XI gene is found on chromosome 4.12, 13
Some patients develop acquired hemophilia. This occurs when a patient's immune system attacks clotting factors VIII14 Acquired hemophilia can be associated with:14

Why is hemophilia more common in those assigned male at birth? The genes for clotting factors sit on the X chromosome, not the Y.1 People with XY chromosomes develop hemophilia if they inherit an altered copy of a gene on their X chromosome. On the other hand, a person with XX chromosomes can inherit an altered copy of a gene on an X chromosome from one parent but receive an unaltered copy on the X chromosome inherited from the other parent. This combination can offer some defense against developing hemophilia.12
People with XX chromosomes who inherit only one altered copy of a gene are known as “carriers.” They sometimes experience hemophilia symptoms and can pass the gene mutations onto their children.1 To develop severe hemophilia C, a person must have parents who both carry the genetic mutation.10 A person can inherit the condition from just one parent, but it’s usually less severe when a patient inherits only one mutated gene.10
The genetic link to hemophilia focuses on two significant risk factors. People are more likely to inherit the genetic mutations that cause hemophilia when they have:2,5
Because the condition is genetic, there’s no way to prevent hemophilia.2 However, patients can take steps to limit the frequency and severity of their bleeding.1,2
Aspirin and NSAIDs (ibuprofen and similar drugs) can worsen bleeding in patients with hemophilia.15,16 Medications designed to prevent blood from clotting can also be problematic for those with hemophilia.16 Consulting a healthcare provider can help with informed decisions.
Brushing regularly can help prevent gum and tooth disease, which can cause excessive bleeding.17
Frequent physical activity strengthens muscles and protects joints. Activities such as swimming, walking, or biking can help, whereas contact sports are not recommended.18,19
Before engaging in physical activity, it can be helpful to talk to a doctor or physical therapist about what protective gear is appropriate.19
Following vaccination schedules is recommended.20
The three most common kinds of hemophilia are:
This type is typically inherited, ranging from mild to severe. A mutation of the F8 gene on the X chromosome causes low production of clotting factor VIII, leading to bleeding in the muscles and joints. Patients with XY chromosomes are more susceptible.8 In the United States, new research shows hemophilia type A affects 1 in every 5,000 births of people assigned male at birth—approximately 400 babies annually.5
Known as Christmas disease or factor IX (FIX) deficiency, this inherited form of hemophilia stems from an F9 gene mutation on the X chromosome.9 This results in a lack of clotting factor IX and, as with hemophilia A, it can cause bleeding in the muscles and joints.1,9 Still, it's four times less common than hemophilia A.1
This type of hemophilia is also called Rosenthal syndrome or factor XI deficiency. Factor XI is responsible for helping to set off a critical chain of events: It’s integral to creating thrombin, the protein that converts fibrinogen to a substance called fibrin. In turn, fibrin holds platelets together to form a blood clot.10 Inconsistent with hemophilia A and B, the mutation that causes hemophilia C is located on chromosome 411 It’s mainly autosomal recessive, meaning both parents must carry the gene for a child to inherit the condition. The deficiency affects people born with XX and XY chromosomes equally. Hemophilia C affects 1 in every 100,000 people. In Israel, hemophilia C affects as many as 8% of Ashkenazi Jews.10
Patients may experience hemophilia signs and symptoms, including:1


Depending on the severity of the case, several complications of hemophilia may arise. Patients should look out for:
The severity of the condition has a large influence over potential life span. Hemophilia patients’ life expectancy is six years shorter on average—however, with the advancements of the past 45 years, those estimates are approaching that of the general population.24
After receiving a hemophilia diagnosis, patients should consider visiting a comprehensive hemophilia treatment center. These facilities are staffed with doctors and nurses specially trained to provide personalized treatment and education on staying healthy and minimizing health risks.1
With adequate treatment, most patients can expect to live a relatively normal life with little impact on daily activities. However, hemophilia management is often more complex for people who develop an inhibitor, an antibody that makes it difficult to control bleeding.25
Several hemophilia treatments are either under investigation or already available.
These therapies replace patients’ missing clotting factors with clotting factor concentrates. Clotting factor concentrates can be administered by injection or infusion.26
There are different types of factor replacement products, including:
Some people develop inhibitors that prevent their bodies from accepting factor treatment products. These patients require special treatment, sometimes in the form of bypassing agents that circumvent the inhibitor-blocked factors and support clot development.25
Several medications and therapies are available for hemophilia treatment, including:26
Life expectancy for people with hemophilia has increased. For example, one study of patients in the Netherlands found that, between 2001 and 2018, people with hemophilia had a median life expectancy of 77 years, which was 6 years lower than the general population of people who were assigned male at birth. This marked an 11-year improvement over the previous hemophilia life-expectancy data, which spanned from 1973 to 1986.24 Patients who receive care in hemophilia treatment centers are 40% less likely to experience death or hospitalization due to their disease.5

Hemophilia affects patients worldwide. A global report from the World Federation of Hemophilia found that 67% of cases occur in low- and lower-middle-income countries. The study also found that hemophilia can negatively impact employment, with 12% of patients reporting that hemophilia led them to part-time work, extended leave, or unemployment.28 Most people with hemophilia report mobility problems, pain, and bleeding incidents.29
Healthcare costs for people with hemophilia can also be significant. In the United States, the average price tag for managing hemophilia B is greater than $200,000 per patient annually, with the cost exceeding $630,000 for patients with severe hemophilia B.30 In Europe, the average annual per-patient cost of severe hemophilia A and B is about €200,000, according to a study that examined costs in France, Germany, Italy, Spain, and the United Kingdom. Drugs accounted for almost 98% of direct costs.31 In Australia, the average annual per-patient cost for moderate to severe hemophilia A is about €74,000.32
Patients and caregivers will understandably have some common questions about the disorder and how to manage it.
Hemophilia is a chromosomally linked recessive disorder, the result of a mutated gene on the X chromosome. Because those assigned male at birth only have one X chromosome, they can develop hemophilia if they inherit the altered gene.2 Carriers, who have only one altered gene, may experience symptoms and pass the mutation down.1
Although comparatively rare,1 people assigned female at birth can inherit hemophilia. A person can inherit X chromosomes with altered copies of genes from both parents. Or a person can inherit an X chromosome with a gene mutation and an X chromosome that does provide protection.12
The genes for clotting factors sit on the X chromosome, not the Y.1 For people with XY chromosomes, inheriting one altered copy of a gene is usually enough to cause the disease. On the other hand, a person with XX chromosomes who inherits an altered copy of a gene on one X chromosome might receive an unaltered copy on the other X chromosome, offering some defense against hemophilia.12
Globally, more than 200,000 people live with some form of hemophilia.3 In the United States, the estimated incidence of hemophilia A is 1 in every 5,617 births of people assigned male at birth, who have XY chromosomes. The estimated incidence of hemophilia B is 1 in every 19,283 births of people with XY chromosomes.7 In one study, patients who were assigned female at birth account for roughly 18% of mild hemophilia cases and less than 1% of severe cases.6
No, hemophilia cannot be prevented, but patients can take action to limit the severity and frequency of bleeding.1,2
Treatment options can help reduce the frequency and severity of bleeding.26
Your doctor will run diagnostic tests, including blood tests to check for clotting factors. Your care team may also conduct genetic testing.5,33
Find a Pfizer clinical trial for hemophilia at PfizerClinicalTrials.com.
Explore hemophilia clinical trials at ClinicalTrials.gov.
Area of Focus: Rare Disease
Hemophilia is a focus of Pfizer’s Rare Disease Therapeutic Area. Visit the Rare Disease Page.
The information contained on this page is provided for your general information only. It is not intended as a substitute for seeking medical advice from a healthcare provider. Pfizer is not in the business of providing medical advice and does not engage in the practice of medicine. Pfizer under no circumstances recommends particular treatments for specific individuals and in all cases recommends consulting a physician or healthcare center before pursuing any course of treatment.