F8 coagulation factor VIII
Also known as: AHF, antihemophilic factor, coagulation factor VIII, procoagulant component, coagulation factor VIII, procoagulant component (hemophilia A), DXS1253E, FA8_HUMAN, Factor VIIIF8B, FVIII, HEMA, procoagulant component.
Approximate pronunciation (generated from the name, not a recording):
- F8 eff-eight
- coagulation factor VIII coagulation factor vee-eye-eye-eye
What this gene does
The F8 gene provides instructions for making a protein called coagulation factor VIII. Coagulation factors are a group of related proteins that are essential for the formation of blood clots. After an injury, clots protect the body by sealing off damaged blood vessels and preventing further blood loss.
Coagulation factor VIII is made chiefly by cells in the liver. This protein circulates in the bloodstream in an inactive form, bound to another molecule called von Willebrand factor, until an injury that damages blood vessels occurs. In response to injury, coagulation factor VIII is activated and separates from von Willebrand factor. The active protein (sometimes written as coagulation factor VIIIa) interacts with another coagulation factor called factor IX. This interaction sets off a chain of additional chemical reactions that form a blood clot.
Source: MedlinePlus Genetics (reviewed 2010-05; source updated 2020-08-18).
Hemophilia A
Approximate pronunciation (generated from the name, not a recording):
- Hemophilia A hemophilia ay
Also known as: Haemophilia, Hemophilia, familial, Hemophilia, hereditary.
The reviewed source page covers hemophilia generally, which includes hemophilia A.
What is Hemophilia A?
Hemophilia is a bleeding disorder that slows the blood clotting process. People with this condition experience prolonged bleeding or oozing following an injury, surgery, or having a tooth pulled. In severe cases of hemophilia, continuous bleeding occurs after minor trauma or even when there is no obvious injury (sometimes called spontaneous bleeding). Serious complications can result from bleeding into the joints, muscles, brain, or other internal organs. Milder forms of hemophilia do not necessarily involve spontaneous bleeding, and the condition may not become apparent until abnormal bleeding occurs following surgery or a serious injury.
The major types of this condition are hemophilia A (also known as classic hemophilia or factor VIII deficiency) and hemophilia B (also known as Christmas disease or factor IX deficiency). Although the two types have very similar signs and symptoms, they are caused by variants (also known as mutations) in different genes. People with an unusual form of hemophilia B, known as hemophilia B Leyden, experience episodes of excessive bleeding in childhood but have few bleeding problems after puberty.
Source: MedlinePlus Genetics (reviewed 2010-05; source updated 2022-05-06).
How it is inherited
Hemophilia A and hemophilia B are inherited in an X-linked recessive pattern. The genes associated with these conditions are located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. A characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.
In females (who have two X chromosomes), a variant would usually have to occur in both copies of the gene to cause the disorder. However, in some instances, one altered copy of the F8 or F9 gene is sufficient, because the X chromosome with the normal copy of the gene is turned off through a process called X-inactivation. X-inactivation occurs early in embryonic development in females. Through this process, one of the two X chromosomes is permanently turned off (inactivated) in somatic cells (cells other than egg and sperm cells). X-inactivation ensures that females, like males, have only one active copy of the X chromosome in each body cell.
Usually X-inactivation occurs randomly, such that each X chromosome is active in about half of the body cells. Sometimes X-inactivation is not random, and one X chromosome is active in more than half of cells. When X-inactivation does not occur randomly, it is called skewed X-inactivation.
In many females with a variant in one copy of the F8 or F9 gene, X-inactivation is random and the chromosome with the normal copy of the gene is turned off in about half of cells. These individuals have about half the usual amount of coagulation factor VIII or coagulation factor IX, which is generally enough for normal clotting. However, in some females with an F8 or F9 gene variant, X-inactivation is skewed, and the chromosome with the normal copy of the gene is turned off in more than half of cells. These individuals can have less coagulation factor VIII or coagulation factor IX than usual and are at risk of abnormal bleeding.
Source: MedlinePlus Genetics (reviewed 2010-05; source updated 2022-05-06).
How common it is
MedlinePlus Genetics Frequency
The two major forms of hemophilia occur much more commonly in males than in females. Hemophilia A is the most common type of the condition; 1 in 4,000 to 1 in 5,000 males worldwide are born with this disorder. Hemophilia B occurs in approximately 1 in 20,000 newborn males worldwide.
Source: MedlinePlus Genetics (reviewed 2010-05; source updated 2022-05-06).
Research studies
85 studies recruiting people with Hemophilia A. Showing the first 5 of 85.
- High-Altitude Hematology Observation-Stem Cell Transplantation (HALO-SCT) (NCT07205523)
- Severe Congenital Hemostatic Defects, Cerebral MIcrobleeds and COGnition (NCT06090201)
- An Open-label, Multicenter Phase I/II Clinical Trial to Evaluate the Safety, Tolerability, Efficacy, and Pharmacokinetic/Pharmacodynamic (PK/PD) Characteristics of SR604 Injection in Patients With Hemophilia A/B and Congenital Factor VII Deficiency (NCT07644832)
- ITI Using SCT800 Alone or Combining Daratumumab in Hemophilia A Adolescents and Adults With High Titer Inhibitor (NCT05888870)
- Longitudinal Cohort of Thrombosis and Hemostasis Diseases (NCT06727669)
See all recruiting studies on ClinicalTrials.gov.
Source: ClinicalTrials.gov (retrieved 2026-10-04).
Family and care
What a diagnosis can mean for a family, and what to ask. This guidance is general, not specific to one gene.
What is a genetic consultation?
A genetic consultation is a health service that provides information and support to people who have, or may be at risk for, genetic conditions. During a consultation, a genetics professional meets with an individual or family to discuss genetic risks or to diagnose, confirm, or rule out a genetic condition.
Genetics professionals include medical geneticists (doctors who specialize in genetics) and genetic counselors (certified healthcare workers with experience in medical genetics and counseling). Other healthcare professionals such as nurses, psychologists, and social workers trained in genetics can also provide genetic consultations.
Consultations usually take place in a doctor’s office, hospital, genetics center, or other type of medical center. These meetings are most often in-person visits with individuals or families, but they are occasionally conducted in a group. Additionally, genetic consultations may be carried out using telemedicine (also known as telehealth), in which the meeting is done from a distance using computers, cameras, videoconferencing tools, or the telephone.
Source: MedlinePlus Genetics.
Why might someone have a genetic consultation?
Individuals or families who are concerned about an inherited condition may benefit from a genetic consultation. The reasons that a person might be referred to a genetic counselor, medical geneticist, or other genetics professional include:
A personal or family history of a genetic condition, birth defect, chromosomal disorder, or hereditary cancer.
Two or more pregnancy losses (miscarriages), a stillbirth, or a baby who died.
A child with a known inherited disorder, a birth defect, intellectual disability, or developmental delay.
A woman who is pregnant or plans to become pregnant at or after age 35. (Some chromosomal disorders occur more frequently in children born to older women.)
Abnormal test results that suggest a genetic or chromosomal condition.
An increased risk of developing or passing on a particular genetic disorder on the basis of a person’s ethnic background.
People related by blood (for example, cousins) who plan to have children together. (A child whose parents are related may be at an increased risk of inheriting certain genetic disorders.)
A person received results from direct-to-consumer genetic testing and they want to discuss the implications of the results.
A genetic consultation is also an important part of the decision-making process for genetic testing. A visit with a genetics professional may be helpful even if testing is not available for a specific condition, however.
Source: MedlinePlus Genetics.
What happens during a genetic consultation?
A genetic consultation provides information, offers support, and addresses a patient’s specific questions and concerns. To help determine whether a condition has a genetic component, a genetics professional asks about a person’s medical history and takes a detailed family health history (a record of health information about a person's immediate and extended family). The genetics professional may also perform a physical examination and recommend appropriate medical tests.
If a person is diagnosed with a genetic condition, the genetics professional provides information about the diagnosis, how the condition is inherited, the chance of passing the condition to future generations, and the options for testing and treatment.
During a consultation, a genetics professional will:
Interpret and communicate complex medical information.
Help each person make informed, independent decisions about their health care and reproductive options.
Respect each person’s individual beliefs, traditions, and feelings.
A genetics professional will NOT:
Tell a person which decision to make.
Coerce a couple about whether or not to have children.
Recommend that a woman continue or end a pregnancy.
Tell someone whether to undergo testing for a genetic disorder.
Source: MedlinePlus Genetics.
What is genetic counseling?
The goal of genetic counseling is to help you learn more about the causes of genetic conditions and how they affect you.
Genetic counselors can: Review your family and medical histories; Explain how genetic conditions are passed down through families; Figure out if you or your family members are at risk for disease; Find and give you information about genetic conditions; Offer guidance to help you make informed choices or life plans; Provide information about testing options and help you decide what is best for you and your family; Help you find referrals to medical specialists, advocacy and support networks, and other resources.
Source: National Society of Genetic Counselors and Genetic Alliance (CC BY; published 2008).
Where to go next
- Hemophilia A: National Hemophilia Foundation — The patient advocacy organization for Hemophilia A.
- Find a Genetic Counselor (NSGC) — Find a genetic counselor near you.
- Search ClinicalTrials.gov for Hemophilia A — Look for studies that are recruiting people with Hemophilia A.
Words you may meet
Some technical words appear in the sections above and in the details below. Here is what they mean, in words from a public genetics glossary.
- Gene
- The gene is considered the basic unit of inheritance. Genes are passed from parents to offspring and contain the information needed to specify physical and biological traits. Most genes code for specific proteins, or segments of proteins, which have differing functions within the body. Humans have approximately 20,000 protein-coding genes. NHGRI Talking Glossary of Genomic and Genetic Terms
- Chromosome
- Chromosomes are threadlike structures made of protein and a single molecule of DNA that serve to carry the genomic information from cell to cell. In plants and animals (including humans), chromosomes reside in the nucleus of cells. Humans have 22 pairs of numbered chromosomes (autosomes) and one pair of sex chromosomes (XX or XY), for a total of 46. Each pair contains two chromosomes, one coming from each parent, which means that children inherit half of their chromosomes from their mother and half from their father. Chromosomes can be seen through a microscope when the nucleus dissolves during cell division. NHGRI Talking Glossary of Genomic and Genetic Terms
- Autosomal Recessive Disorder
- Autosomal recessive is a pattern of inheritance characteristic of some genetic disorders. “Autosomal” means that the gene in question is located on one of the numbered, or non-sex, chromosomes. “Recessive” means that two copies of the mutated gene (one from each parent) are required to cause the disorder. In a family where both parents are carriers and do not have the disease, roughly a quarter of their children will inherit two disease-causing alleles and have the disease. By contrast, an autosomal dominant disorder requires only a single copy of the mutated gene from one parent to cause the disorder. Sickle cell anemia is an example of an autosomal recessive genetic disorder. NHGRI Talking Glossary of Genomic and Genetic Terms
- Autosomal Dominant Disorder
- Autosomal dominant is a pattern of inheritance characteristic of some genetic disorders. “Autosomal” means that the gene in question is located on one of the numbered, or non-sex, chromosomes. “Dominant” means that a single copy of the mutated gene (from one parent) is enough to cause the disorder. A child of a person affected by an autosomal dominant condition has a 50% chance of being affected by that condition via inheritance of a dominant allele. By contrast, an autosomal recessive disorder requires two copies of the mutated gene (one from each parent) to cause the disorder. Huntington’s disease is an example of an autosomal dominant genetic disorder. NHGRI Talking Glossary of Genomic and Genetic Terms
- Mitochondrial DNA
- Mitochondrial DNA is the circular chromosome found inside the cellular organelles called mitochondria. Located in the cytoplasm, mitochondria are the site of the cell’s energy production and other metabolic functions. Offspring inherit mitochondria — and as a result mitochondrial DNA — from their mother. NHGRI Talking Glossary of Genomic and Genetic Terms
- Genetic Imprinting
- Genomic imprinting is the process by which only one copy of a gene in an individual (either from their mother or their father) is expressed, while the other copy is suppressed. Unlike genomic mutations that can affect the ability of inherited genes to be expressed, genomic imprinting does not affect the DNA sequence itself. Instead, gene expression is silenced by the epigenetic addition of chemical tags to the DNA during egg or sperm formation. Epigenetic tags on imprinted genes usually stay in place for the life of the individual. NHGRI Talking Glossary of Genomic and Genetic Terms
- Protein
- Proteins are large, complex molecules that play many important roles in the body. They are critical to most of the work done by cells and are required for the structure, function and regulation of the body’s tissues and organs. A protein is made up of one or more long, folded chains of amino acids (each called a polypeptide), whose sequences are determined by the DNA sequence of the protein-encoding gene. NHGRI Talking Glossary of Genomic and Genetic Terms
- Mutation
- A mutation is a change in the DNA sequence of an organism. Mutations can result from errors in DNA replication during cell division, exposure to mutagens or a viral infection. Germline mutations (that occur in eggs and sperm) can be passed on to offspring, while somatic mutations (that occur in body cells) are not passed on. NHGRI Talking Glossary of Genomic and Genetic Terms
- Pathogenic Variant
- A pathogenic variant is a genomic variant that may increase a person’s risk of developing a condition, disorder or disease. In many cases, carrying a pathogenic variant does not guarantee that a person will develop the specific condition but increases the risk for it. Pathogenic variants can be inherited from a parent or can occur spontaneously due to factors such as environmental exposure and aging. NHGRI Talking Glossary of Genomic and Genetic Terms
- Genetic Testing
- Genetic testing is the use of a laboratory test to examine an individual’s DNA for variations, typically performed in the context of medical care, ancestry studies or forensics. In a medical setting, the results of a genetic test can be used to confirm or rule out a suspected genetic disease. Results may also be used to determine the likelihood of parents passing on a genetic mutation to their offspring. Genetic testing may be performed prenatally or after birth. Genetic testing is also used to study the genomes of tumors in cancer cases. NHGRI Talking Glossary of Genomic and Genetic Terms
- Carrier
- A carrier, as related to genetics, is an individual who “carries” and can pass on to its offspring a genomic variant (allele) associated with a disease (or trait) that is inherited in an autosomal recessive or sex-linked manner, and who does not show symptoms of that disease (or features of that trait). The carrier has inherited the variant allele from one parent and a normal allele from the other parent. Any offspring of carriers is at risk of inheriting a variant allele from their parents, which would result in that child having the disease (or trait). NHGRI Talking Glossary of Genomic and Genetic Terms
- Allele
- An allele is one of two or more versions of DNA sequence (a single base or a segment of bases) at a given genomic location. An individual inherits two alleles, one from each parent, for any given genomic location where such variation exists. If the two alleles are the same, the individual is homozygous for that allele. If the alleles are different, the individual is heterozygous. NHGRI Talking Glossary of Genomic and Genetic Terms
- Mendelian Inheritance
- Mendelian inheritance refers to certain patterns of how traits are passed from parents to offspring. These general patterns were established by the Austrian monk Gregor Mendel, who performed thousands of experiments with pea plants in the 19th century. Mendel’s discoveries of how traits (such as color and shape) are passed down from one generation to the next introduced the concept of dominant and recessive modes of inheritance. NHGRI Talking Glossary of Genomic and Genetic Terms
Details you may see on a test report
These names and numbers are the technical ones doctors and labs use. You do not need to memorize them.
Location
This is where the gene sits on its chromosome, so you can match it to coordinates on a test report.
Xq28 · GRCh38 chrX:154,835,788–155,026,940
Open in Ensembl (primary) or UCSC Genome Browser (secondary).
Source: HGNC (HGNC:3546).
Recommended transcript
This is the reference transcript labs use when they report a change in this gene.
- MANE Select
NM_000132.4(RefSeq) /ENST00000360256.9(Ensembl)
Source: NCBI MANE.
Protein domains
These are the working parts of the protein, with the amino-acid positions each one covers.
- Coagulation factor 5/8, C-terminal domain — amino acids 2039–2188, 2192–2345
- Multicopper oxidase-like, C-terminal — amino acids 1918–2037
- Multicopper oxidase-like, N-terminal — amino acids 90–198, 453–572
Protein structure
This lets you look at the protein's 3D shape if you want to.
View the predicted structure in AlphaFold, or search the PDB for solved structures.
Source: UniProt (P00451).
Reported gene variants
ClinVar collects gene variants people have reported; it is a place to search, not a list on this page.
This page does not list individual variants. Search ClinVar for F8 instead.
Source: ClinVar.
What this page is not
This page is for education only. It is not medical advice, and it is not a diagnosis or a treatment plan. Talk with a doctor or a genetic counselor about your family's situation.