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The frequency of the 59 variants identified in 76 Chinese hemophilia B (HB) pedigrees: 38 (64.41%) were missense mutation, nine (15.25%) were nonsense mutations

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https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7667291/

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picture of a karyotype from some with hemophilia

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picture of a karyotype from some with hemophilia

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The most effective way to treat it is to replace the missing blood clotting factor so that the blood will be able to clot properly.

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Centers for Disease Control and Prevention

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Learn about treatments for hemophilia and hemophilia treatment centers (HTCs).

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Bleeding into the joints.

Lots of bruising or hematoma.

Hard to stop bleeding after losing a tooth.

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Centers for Disease Control and Prevention

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Hemophilia is usually an inherited bleeding disorder in which the blood does not clot properly. This can lead to spontaneous bleeding as well as bleeding following injuries or surgery. Blood contains many proteins called clotting factors that can help to stop bleeding. People with hemophilia have low levels of either factor VIII (8) or factor IX (9). The severity of hemophilia that a person has is determined by the amount of factor in the blood. The lower the amount of the factor, the more likely it is that bleeding will occur which can lead to serious health problems.

In rare cases, a person can develop hemophilia later in life. The majority of cases involve middle-aged or elderly people, or young women who have recently given birth or are in the later stages of pregnancy. This condition often resolves with appropriate treatment.

Causes

Hemophilia is caused by a mutation or change, in one of the genes, that provides instructions for making the clotting factor proteins needed to form a blood clot. This change or mutation can prevent the clotting protein from working properly or to be missing altogether. These genes are located on the X chromosome. Males have one X and one Y chromosome (XY) and females have two X chromosomes (XX). Males inherit the X chromosome from their mothers and the Y chromosome from their fathers. Females inherit one X chromosome from each parent.

The X chromosome contains many genes that are not present on the Y chromosome. This means that males only have one copy of most of the genes on the X chromosome, whereas females have 2 copies. Thus, males can have a disease like hemophilia if they inherit an affected X chromosome that has a mutation in either the factor VIII or factor IX gene. Females can also have hemophilia, but this is much rarer. In such cases both X chromosomes are affected or one is affected and the other is missing or inactive. In these females, bleeding symptoms may be similar to males with hemophilia.

A female with one affected X chromosome is a "carrier" of hemophilia. Sometimes a female who is a carrier can have symptoms of hemophilia. In addition, she can pass the affected X chromosome with the clotting factor gene mutation on to her children. Learn more about the inheritance pattern for hemophilia.

Even though hemophilia runs in families, some families have no prior history of family members with hemophilia. Sometimes, there are carrier females in the family, but no affected boys, just by chance. However, about one-third of the time, the baby with hemophilia is the first one in the family to be affected with a mutation in the gene for the clotting factor.

Hemophilia can result in:

Bleeding within joints that can lead to chronic joint disease and pain

Bleeding in the head and sometimes in the brain which can cause long term problems, such as seizures and paralysis

Death can occur if the bleeding cannot be stopped or if it occurs in a vital organ such as the brain.

Tips for Healthy Living

Types

There are several different types of hemophilia. The following two are the most common:

Hemophilia A (Classic Hemophilia)
This type is caused by a lack or decrease of clotting factor VIII.

Hemophilia B (Christmas Disease)
This type is caused by a lack or decrease of clotting factor IX.

Signs and Symptoms

Common signs of hemophilia include:

Bleeding into the joints. This can cause swelling and pain or tightness in the joints; it often affects the knees, elbows, and ankles.

Bleeding into the skin (which is bruising) or muscle and soft tissue causing a build-up of blood in the area (called a hematoma).

Bleeding of the mouth and gums, and bleeding that is hard to stop after losing a tooth.

Bleeding after circumcision (surgery performed on male babies to remove the hood of skin, called the foreskin, covering the head of the penis).

Bleeding after having shots, such as vaccinations.

Bleeding in the head of an infant after a difficult delivery.

Blood in the urine or stool.

Frequent and hard-to-stop nosebleeds.

Who is Affected

Hemophilia occurs in about 1 of every 5,000 male births. Based on recent study that used data collected on patients receiving care in federally funded hemophilia treatment centers during the period 2012-2018, about 20,000 as many as 33,000 males in the United States are living with the disorder. Hemophilia A is about four times as common as hemophilia B, and about half of those affected have the severe form. Hemophilia affects people from all racial and ethnic groups.

Diagnosis

Many people who have or have had family members with hemophilia will ask that their baby boys get tested soon after birth.
About one-third of babies who are diagnosed with hemophilia have a new mutation not present in other family members. In these cases, a doctor might check for hemophilia if a newborn is showing certain signs of hemophilia.
To make a diagnosis, doctors would perform certain blood tests to show if the blood is clotting properly. If it does not, then they would do clotting factor tests, also called factor assays, to diagnose the cause of the bleeding disorder. These blood tests would show the type of hemophilia and the severity.
Learn more about diagnosis
Treatment

The best way to treat hemophilia is to replace the missing blood clotting factor so that the blood can clot properly. This is done by infusing (administering through a vein) commercially prepared factor concentrates. People with hemophilia can learn how to perform these infusions themselves so that they can stop bleeding episodes and, by performing the infusions on a regular basis (called prophylaxis), can even prevent most bleeding episodes.
Good quality medical care from doctors and nurses who know a lot about the disorder can help prevent some serious problems. Often the best choice for care is to visit a comprehensive Hemophilia Treatment Center (HTC). An HTC not only provides care to address all issues related to the disorder, but also provides health education that helps people with hemophilia stay healthy.
Learn more about treatment
Inhibitors

About 15-20 percent of people with hemophilia develop an antibody (called an inhibitor) that stops the clotting factors from being able to clot the blood and stop bleeding. Treatment of bleeding episodes becomes extremely difficult, and the cost of care for a person with an inhibitor can skyrocket because more clotting factor or a different type of clotting factor is needed. People with inhibitors often experience more joint disease and other problems from bleeding that result in a reduced quality of life.
Learn more about inhibitors

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What is Hemophilia? Hemophilia is an inherited bleeding disorder in which the blood does not clot properly. The mission of CDC's Division of Blood Disorders is to reduce the morbidity and mortality from blood disorders through comprehensive public health practice.

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hemophilia is the inability for blood to clot cuts or scrape

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It effects about 10 in 100,000 people.

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Overview

What is hemophilia?

Hemophilia is a rare, inherited blood disorder that causes your blood to clot less, which results in an increased risk of bleeding or bruising.

Hemophilia happens because your body doesn't make enough protein (clotting factors) to help your blood form clots. Clotting factors are proteins in your blood. They work with your platelets to form blood clots that control bleeding. Low clotting factor levels increase bleeding risk.

There are several types of hemophilia. Hemophilia may be severe, moderate or mild based on the amount of clotting factor in your blood.

Healthcare providers treat this condition by replacing the missing clotting factor. There isn't a cure for hemophilia, but people who receive treatment generally live nearly as long as people who don't have hemophilia. Providers are researching gene therapy and gene replacement therapy as new ways to treat and possibly cure hemophilia.

Can people develop hemophilia?

Yes, but that rarely happens. Acquired hemophilia, or hemophilia that isn't inherited, develops when autoantibodies start to attack a specific clotting factor. ( Antibodies are protective proteins your immune system makes. Autoantibodies attack antibodies, essentially attacking your body's own cells, tissues and proteins.)

Is hemophilia a common disease?

No, it's not. According to the U.S. Centers for Disease Control and Prevention (CDC) in August 2022, about 33,000 people in the U.S. have hemophilia. Hemophilia typically affects men and people assigned male at birth (AMAB). Rarely, women and people assigned female at birth (AFAB) may have clotting factor levels that are so low that they develop symptoms such as having very heavy periods.

What are hemophilia types?

There are three types of hemophilia:

Hemophilia A: This is the most common type of hemophilia. It happens when you don't have enough clotting factor 8 (factor VIII). The CDC estimates about 10 in 100,000 people have hemophilia A.

Hemophilia B: Hemophilia B happens when you don't have enough clotting factor 9 (factor IX.) The CDC estimates about 3 in 100,000 people in the U.S. have hemophilia B.

Hemophilia C: Hemophilia C is also known as factor 11 (factor XI) deficiency. This hemophilia type is very rare, affecting 1 in 100,000 people.

Is hemophilia a serious illness?

It can be. People with severe hemophilia may develop life-threatening bleeding, but they're more likely to develop bleeding in their muscles and joints.

Symptoms and Causes

What are hemophilia symptoms?

The most significant symptom is unusual or excessive bleeding or bruising.

People with hemophilia may develop large bruises after minor injuries. This is a sign of bleeding under their skin.

They may bleed for an unusually long time, whether that's bleeding after surgery, bleeding after dental treatment or simply bleeding from a cut finger.

They may start bleeding for no apparent reason, such as sudden bloody noses.

How much bruising or bleeding people have depends on whether they have severe, moderate or mild hemophilia:

People with severe hemophilia often have spontaneous bleeding or bleeding for no apparent reason.

People with moderate hemophilia who have serious injuries may bleed for an unusually long time.

People with mild hemophilia may have unusual bleeding, but only after major surgery or injury.

Other symptoms may include:

Joint pain from internal bleeding. Joints in your ankles, knees, hips and shoulders may ache, swell or feel hot to the touch.

Bleeding into your brain. People with severe hemophilia very rarely develop life-threatening bleeding into their brains. Brain bleeds may cause persistent headaches, double vision or make you feel very sleepy. If you have hemophilia and have these symptoms, get help right away.

What are hemophilia symptoms in babies and children?

Sometimes, babies assigned male at birth with hemophilia are diagnosed because they bleed more than usual after being circumcised. Other times, children develop symptoms a few months after they're born. Common symptoms include:

Bleeding: Babies and toddlers may bleed from their mouths after minor injuries, like bumping their mouths on a toy.

Swollen lumps on their heads: Babies and toddlers who bump their heads often develop goose eggs - large round lumps on their heads.

Fussiness, irritability or refusal to crawl or walk: These symptoms may happen if babies and toddlers have internal bleeding into a muscle or joint. They may have areas on their bodies that look bruised and swollen, feel warm to your touch or make your child hurt when you gently touch the area.

Hematomas: A hematoma is a mass of congealed blood that gathers under babies' or toddlers' skin. Babies and toddlers may develop hematomas after receiving an injection.

What causes hemophilia?

Certain genes create clotting factors. In inherited hemophilia, the genes carrying instructions for making normal clotting factors mutate or change. The mutated genes may give instructions that end up making abnormal clotting factors or not enough clotting factors. That said, about 20% of all hemophilia cases are spontaneous, meaning someone has the disease even though there's no family history of abnormal bleeding.

How do people inherit hemophilia?

Hemophilia A and B are both sex-linked disorders that are inherited in an X-linked recessive manner. Here's how that happens:

Everyone receives one set of chromosomes from their biological mother and one set of chromosomes from their biological father. If you get an X chromosome from your mother and an X chromosome from your father, you are assigned female at birth. If you get an X chromosome from your mother and a Y chromosome from your father, you are assigned male at birth. In other words, a mother will always pass an X chromosome to her offspring. The father will determine the assigned sex at birth by providing either an X or a Y chromosome.

If a woman has an abnormal factor gene on one of their X chromosomes, they carry hemophilia but may not have symptoms. That's because there's a normal factor gene on their second X chromosome.

If a woman who carries an X chromosome with a defective gene for producing factor 8 (or factor 9) has a male child, that child has a 50% chance of inheriting the X chromosome that carries the abnormal factor gene.

If that same woman has a female child, that child has a 50% chance of inheriting the faulty chromosome and abnormal factor gene. That child likely wouldn't have symptoms because they'll also inherit a normal X chromosome from their father.

In other words, a woman who inherits a faulty X chromosome and abnormal factor gene will carry hemophilia. They may not have symptoms, but they can pass the condition on to their children. There's a 50% chance that any children they have - boys or girls - will inherit hemophilia. Boys who do inherit hemophilia are more likely to have severe symptoms. That's because they don't get a healthy X chromosome from their father.

Do women ever develop hemophilia symptoms?

They can, but those symptoms tend to be mild. For example, a woman carrying the hemophilia gene may not have the normal clotting factors or not enough clotting factors. When that happens, they may have unusually heavy menstrual periods and they may bruise easily. They may bleed more after childbirth and they may develop joint problems if they have internal bleeding into their joints.

Diagnosis and Tests

How do healthcare providers diagnose hemophilia?

A healthcare provider will start by doing a complete history and physical examination. If you have hemophilia symptoms, the provider will ask about your family's medical history. Providers may do the following tests:

Complete blood count (CBC): Providers use this test to measure and study blood cells.

Prothrombin time (PT) test: Providers use this test to see how quickly your blood clots.

Activated partial thromboplastin time test: This is another blood test to time blood clot formation.

Specific clotting factor test(s): This blood test show levels of specific clotting factor levels (such as factor 8 and factor 9).

What are clotting factor levels?

Clotting factors help control bleeding. Healthcare providers categorize hemophilia as being mild, moderate or severe based on the amount of clotting factors in your blood:

People who have 5% to 30% of the normal amount of clotting factors in their blood have mild hemophilia.

People with 1% to 5% of the normal level of clotting factors have moderate hemophilia.

People with less than 1% of the normal clotting factors have severe hemophilia.

Management and Treatment

How do healthcare providers treat hemophilia?

They treat hemophilia by boosting clotting factor levels or replacing missing clotting factors (replacement therapy).

In replacement therapy, you receive human plasma concentrates or lab-made (recombinant) clotting factors. In general, only people with severe hemophilia need regular replacement therapy. People with mild or moderate hemophilia who need surgery may receive replacement therapy. They may also receive antifibrinolytics, a medication that keeps blood clots from breaking down.

Blood factor concentrates are made from donated human blood that's been treated and screened to reduce the risk of transmitting infectious diseases, such as hepatitis and HIV. People receive replacement factors via intravenous infusion (IV).

If you have severe hemophilia and frequent bleeding episodes, your healthcare provider may prescribe prophylactic factor infusions to prevent bleeding.

What are treatment complications?

Some people who have replacement therapy develop antibodies, called inhibitors, which attack the clotting factors that control bleeding. Healthcare providers use a technique called immune tolerance induction (ITI). ITI involves clotting factors given on a daily basis to bring down inhibitor levels. ITI may be a long-term treatment, and some people may need this treatment for months or years.

Prevention

Can people prevent hemophilia?

No, they can't. If you have hemophilia and have children, your healthcare provider may recommend genetic testing so you and your children know whether they might pass hemophilia on to their children.

Outlook / Prognosis

What can I expect if I have hemophilia?

If you have hemophilia, you'll need medical treatment for the rest of your life. How much treatment you'll need depends on your condition type, severity and if you develop inhibitors.

What is the lifespan expectancy for someone with hemophilia?

According to 2012 data from the World Federation of Hemophilia, the lifespan for men and people AMAB with hemophilia is about 10 years fewer than the lifespan for men/people AMAB without hemophilia. The federation also states that children diagnosed with and treated for hemophilia have a normal life expectancy.

But everyone is different. What's true for one person with hemophilia may not be true for others. If you or your child has hemophilia, ask your provider what you can expect. They know your/your child's situation, including overall health, and they're your best resource for information.

Living With

How do I take care of myself?

People with hemophilia may need ongoing medical treatment to prevent bleeding. They may need to avoid certain activities and medications. But there are many things you can do to manage the impact hemophilia may have on the quality of your life.

Activities to avoid

Bumps, falls and hard knocks that other people shake off may be serious issues for people with hemophilia. They may need to avoid activities that increase their risk of being hit or falling down after being hit. Examples include:

Playing football, hockey or rugby.

Participating in boxing or wrestling.

Riding motorcycles.

Riding skateboards.

Participating in other sports such as soccer, basketball and baseball may increase your risk of injuries. Ask your healthcare provider what you can do, like using protective gear, so you can play these sports.

Medications to avoid

Pain medications like aspirin, ibuprofen and naproxen keep your blood from clotting well. You should also avoid anticoagulants such as heparin or warfarin.

Activities and actions to improve quality of life

There are many things you can do to limit the impact hemophilia may have on your quality of life:

Develop an exercise routine: You may worry about hurting yourself during exercise. Talk to your provider about ways to reduce the risk of bleeding while staying active.

Manage your stress: Hemophilia is a lifelong illness. It may take extra effort to balance your obligations to your family and work.

Have good dental hygiene: Brushing, flossing and regular visits to your dentist reduce the risk that you'll need dental treatment that may cause bleeding. Be sure your dentist knows about your medical condition.

Aim for a weight that's healthy for you: Managing your weight may help if you're having trouble getting around because internal bleeding damaged your joints.

Educate those around you: If you have a severe form of hemophilia, you may have spontaneous bleeding that's hard to control even if you're taking medication. Make sure your family knows what to do if you have spontaneous bleeding. If your child has hemophilia, make sure care providers and school officials know what to do if your child has bleeding issues.

When should I see my healthcare provider?

Contact your healthcare provider if you notice changes in your body, like increased bleeding or bruising.

When should I go to the emergency room?

You should go to the emergency room if:

You have severe headaches or double vision. These symptoms may mean you have bleeding in your brain.

You have joint swelling and/or pain and you don't have access to factor replacement medication.

What questions should I ask my healthcare provider?

If you or your child is diagnosed with hemophilia, you may want to ask your provider some of the following questions:

What type of hemophilia do I/does my child have?

What treatments do you recommend?

What are treatment side effects?

Will I/my child always need treatment?

What activities will I/my child need to avoid?

What medications will I/my child need to avoid?

What are things I can do to manage the impact this condition may have on my/my child's life?

A note from Cleveland Clinic
Hemophilia is a rare, inherited blood disorder that changes people's lives. People with hemophilia may need medical treatment for the rest of their lives. Parents of children with hemophilia may feel anxious about protecting them from accidental injuries. They may worry about helping their children learn to live with hemophilia. At this time, healthcare providers can't cure hemophilia. They can provide treatment to prevent or reduce hemophilia symptoms. And they can make recommendations for steps people can take to limit hemophilia's impact on daily life.

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Hemophilia is a rare, inherited blood disorder that causes your blood to clot less, which results in an increased risk of bleeding or bruising. Hemophilia happens because your body doesn't make enough protein (clotting factors) to help your blood form clots. Clotting factors are proteins in your blood.

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i cam across 20 other sites but i don't have room for that

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Hemophilia is a recessive sex-linked trait. So the gene is carried on the X chromosome.

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the CDC is researching hemophilia

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Centers for Disease Control and Prevention

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People with hemophilia can experience complications, such as joint disease and inhibitors, that can affect overall health. CDC collaborates with public and private organizations to conduct research to better understand hemophilia. Results from this research are used to implement prevention programs to help reduce complications and improve the quality of life.

CDC conducts research to:

Learn more about the extent of bleeding disorders and risk factors for complications.

Design and implement interventions that will help prevent complications.

Create and deliver health promotion messages to help people make informed decisions about their own health care.

Identify new genetic markers of risk factors through lab analysis.

Following are some areas of research in hemophilia:

Universal Data Collection System

One of the major challenges facing researchers and scientists who work on rare disorders such as hemophilia is the lack of access to uniform health data. To address this issue and advance health research, CDC supported and coordinated a public health surveillance project, the Universal Data Collection (UDC) system. From 1998-2011, UDC operated through a national network of specialized hemophilia treatment centers (HTCs). Overall, about 80% of hemophilia patients who received care in HTCs participated in UDC.

Through UDC, a consistent set of health-monitoring data was collected from people with hemophilia and other bleeding disorders. The data collected can be used to determine rates and severity of disease complications, describe treatment and care patterns, assess quality of life, and determine health issues for further study.

UDC collected data from:

People with hemophilia and people with rare bleeding disorders

Women and girls with bleeding disorders

Children under 2 years of age with bleeding disorders

People with inhibitors

UDC also monitored the hemophilia population for blood-borne infections and stored blood specimens for future research on emerging infectious diseases.

A new initiative, Community Counts- Registry for Bleeding Disorders Surveillance, will build on the past work of the UDC and continue surveillance of this population.
Learn more about UDC
Hemophilia Inhibitor Research Study

People with hemophilia lack a protein that is necessary for normal blood clotting. As many as one third of people with hemophilia develop an antibody-called an inhibitor-to the blood products that they use to stop or prevent a bleeding episode. Treatment of bleeding becomes extremely difficult, and the cost of care can skyrocket. In addition, people with inhibitors are at increased risk for joint disease and other complications from bleeding resulting in a reduced quality of life. In the Inhibitor Study, researchers are looking at why some people develop inhibitors. CDC hopes that better understanding the causes of inhibitors will help us learn how to prevent them.
Learn more about inhibitors
CDC Hemophilia A and Hemophilia B Mutation Project (CHAMP and CHBMP)

Hemophilia is caused by changes (mutations) in the genes for clotting factors VIII and IX. These mutations result in a decrease in the amount of factor, which is necessary for normal blood clotting. A deficiency of factor VIII is called hemophilia A and a deficiency of factor IX is called hemophilia B. As part of the Inhibitor Study, the Centers for Disease Control and Prevention (CDC) has gathered a list of all of the mutations reported to cause hemophilia worldwide. More than 2,000 mutations have been reported in the factor VIII gene and more than 1,000 in factor IX. The mutation that a person has determines how much clotting factor is produced and how well it works. Knowing the mutation that a person with hemophilia has is important for genetic testing of family members. It also can help predict how likely it is that a person will develop an inhibitor. Future treatments for people with hemophilia might work better for some types of mutations than for others.
Learn more about CHAMP and CHBMP
Range of Motion Study Among the General Population

People with hemophilia may develop chronic joint disease from repeated bleeding into their joints. Over time, the joint disease results in decreased mobility of the joints. People without hemophilia also lose mobility in their joints with aging. However, there are very few studies of joint mobility over time in people without hemophilia. To have a baseline with which to compare people with hemophilia, the joints of more than 600 people in the general population were measured as part of the normal range of motion study. Data from this study provides a baseline to learn more about loss of mobility due to joint bleeding in people with hemophilia.

Healthy Weight Programs

Maintaining a healthy weight is particularly important for people with hemophilia. Those who are overweight are more likely to have decreased movement in their joints. In addition, the dosage of treatment product is determined by body weight. Therefore, overweight people with hemophilia need a larger dose of treatment product, resulting in a higher cost of care.

CDC is conducting research with health care providers at hemophilia treatment centers (HTCs) to better understand their level of awareness on issues of healthy weight. This project aims to determine:

How BMI is measured and interpreted

What actions are taken if a patient is at risk of being overweight or obese

What perceptions HTC staff may have about healthy weight

How HTC staff can influence a positive outcome for people who receive comprehensive care in an HTC

Evaluation of the National Hemophilia Foundation's National Prevention Program

The National Hemophilia Foundation's (NHF) National Prevention Program called Do the 5! was developed in 2000 to help people with bleeding disorders prevent or reduce the complications of those disorders.
To evaluate the Program, recently collected data on knowledge about, attitudes toward, and behaviors associated with key prevention activities among youth and adults with hemophilia will be compared to similar data that was collected prior to the start of the Program. That survey focused on knowledge about, attitudes toward, and behaviors associated with key prevention activities among youth and adults with hemophilia.

Additionally, data were collected on how the national Do the 5! prevention campaign messages were disseminated and how well consumers were able to recall the messages. This research was conducted by Macro International through telephone surveys targeting adult men with hemophilia, parents of sons with hemophilia aged 9 years or younger, and youth aged 13-21 with hemophilia. Through this evaluation, CDC will learn more about the impact of the National Prevention Program and the extent that target audience members are aware of and able to recall the prevention messages of the Do the 5! campaign.

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People with hemophilia can experience complications, such as joint disease and inhibitors, that can affect overall health. CDC collaborates with public and private organizations to conduct research to better understand hemophilia. Results from this research are used to implement prevention programs to help reduce complications and improve the quality of life.

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The exact name is factor VIII (8) deficiency.

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What Is Hemophilia A?

Hemophilia A, also called factor VIII (8) deficiency or classic hemophilia, is a genetic disorder caused by missing or defective factor VIII (FVIII), a clotting protein. Although it is passed down from parents to children, about 1/3 of cases found have no previous family history.

According to the US Centers for Disease Control and Prevention (CDC), hemophilia occurs in approximately 1 in 5,617 live male births. There are between 30,000 - 33,000 males with hemophilia in the US*. More than half of people diagnosed with hemophilia A have the severe form. Hemophilia A is four times as common as hemophilia B. Hemophilia affects all races and ethnic groups.

Learn more about how blood clots at NHF's Steps for Living..

The Genetics of Hemophilia

Hemophilia A is an inheritable disease, meaning it is passed down from parents to children. The X and Y chromosomes are called sex chromosomes. The gene for hemophilia is carried on the X chromosome. Hemophilia is inherited in an X-linked recessive manner. Females inherit two X chromosomes, one from their mother and one from their father (XX). Males inherit an X chromosome from their mother and a Y chromosome from their father (XY). That means if a son inherits an X chromosome carrying hemophilia from his mother, he will have hemophilia. It also means that fathers cannot pass hemophilia on to their sons.

But because daughters have two X chromosomes, even if they inherit the hemophilia gene from their mother, most likely they will inherit a healthy X chromosome from their father and not have hemophilia. A daughter who inherits an X chromosome that contains the gene for hemophilia is called a carrier. She can pass the gene on to her children. Many women who carry the hemophilia gene also have low factor expression, which can result in heavy menstrual bleeding, easy bruising, and joint bleeds. Some women who have the hemophilia gene have factor expression low enough to be diagnosed with hemophilia.

For a female carrier, there are four possible outcomes for each pregnancy:
1. A girl who is not a carrier
2. A girl who is a carrier
3. A boy without hemophilia
4. A boy with hemophilia

Severity

(percentage breakdown of overall hemophilia population by severity)

* Severe (factor levels less than 1%) represent approximately 60% of cases
* Moderate (factor levels of 1-5%) represent approximately 15% of cases
* Mild (factor levels of 6%-30%) represent approximately 25% of cases

What are the Symptoms of Hemophilia A?

People with hemophilia A bleed longer than other people. Bleeds can occur internally, into joints and muscles, or externally, from minor cuts, dental procedures, or injuries. How often a person bleeds and the severity of those bleeds depends on how much FVIII a person produces naturally.

Normal levels of FVIII range from 50% to 150%. Levels below 50% - or half of what is needed to form a clot - determine a person's symptoms.

* Mild hemophilia A: 6% up to 49% of FVIII in the blood. People with mild hemophilia A generally experience bleeding typically only after serious injury, trauma, or surgery. In many cases, mild hemophilia is not diagnosed until an injury, surgery or tooth extraction results in prolonged bleeding. The first episode may not occur until adulthood. Women with mild hemophilia often experience heavy menstrual bleeding, and can hemorrhage (bleed extensively) after childbirth.
* Moderate hemophilia A: 1% up to 5% of FVIII in the blood. People with moderate hemophilia A tend to have bleeding episodes after injuries.
* Severe hemophilia A. <1% of FVIII in the blood. People with severe hemophilia A experience bleeding following an injury and may have frequent spontaneous bleeding episodes - bleeds that occur without obvious cause - often into their joints and muscles. Many males with severe hemophilia are diagnosed due to bleeding after circumcision.

Diagnosis of Hemophilia A

Doctors will perform tests that evaluate how long it takes for the blood to clot to determine if someone has hemophilia. A clotting factor test, called an assay, will show the type of hemophilia and the severity, or how much clotting factor the person produces on their own.

Most people who have a family history of hemophilia will ask that their baby boys be tested soon after birth to see if they have hemophilia. If there is no family history of hemophilia, people often notice bleeding that takes longer to stop or lots of bruising. Many babies born with severe hemophilia are diagnosed if there is prolonged bleeding after circumcision.

For girls, it often takes seeing worsening of symptoms for the diagnosis process to begin. Most girls are not tested for hemophilia before puberty. Heavy periods are a symptom of a bleeding disorder in women and girls. If there is a known family history, it is important to monitor for symptoms. It is recommended that women who have a family history of hemophilia get tested before getting pregnant, to help prevent complications during childbirth.

The best place for patients with hemophilia to be diagnosed and treated is at one of the federally funded hemophilia treatment centers (HTCs) that are spread throughout the country. HTCs provide comprehensive care from skilled hematologists and other professional staff, including nurses, physical therapists, social workers and sometimes dentists, dieticians and other healthcare providers, including specialized labs for more accurate lab testing.

Find a hemophilia treatment center near you.

How is Hemophilia A Treated?

Most treatments for hemophilia A focus on replacing the missing protein, FVIII (8), so a person can form a clot, and so reduce or eliminate the bleeds associated with the disorder. Treatments that work to prevent bleeding through new mechanisms have recently come to the market or are in clinical trials. People with hemophilia A have several different medication options for treatment.

Learn about treatment options for hemophilia.
Living with Hemophilia A

There's a lot to know about living with a bleeding disorder like hemophilia A. Visit NHF's Steps for Living to explore resources, tools, tips and videos on living with hemophilia A through all life stages. Organized by life stages, Steps for Living provides information on recognizing the signs of bleeds in children, help on navigating school issues, how to exercise safely, helping teens manage their bleeding disorder, information on workplace accommodations, and much more. There are downloadable checklists, toolkits, videos, and more.

Explore NHF's Steps for Living to learn more about living with hemophilia A.
*"Occurrence rates of haemophilia among males in the United States based on surveillance conducted in specialized haemophilia treatment centres," Soucie et al

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Hemophilia A | National Hemophilia Foundation

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Hemophilia A, also called factor VIII (8) deficiency or classic hemophilia, is a genetic disorder caused by missing or defective factor VIII (FVIII), a clotting protein. Although it is passed down from parents to children, about 1/3 of cases found have no previous family history.