The FGF5 gene helps control how long hair stays in its growing phase. If it does not work as expected, hair may keep growing longer than usual, which can lead to very long scalp hair or extra hair growth on the eyelashes, eyebrows, or body. Some people first learn about this gene when a genetic test looks at inherited reasons for unusual hair length. Most variants in this gene are simply part of normal hair diversity.
What is a gene?
Within DNA, a gene is a stretch that holds instructions your cells use to make molecules or regulate processes in the body. Some genes give the directions for making proteins, the parts of cells that do the work. Others mainly control when certain processes occur, where they take place, and how strongly they operate. Taken together, genes affect how the body develops and works, and they can also influence how you respond to food, stress, or medications. For a deeper look at this topic, you can find more in the LearnHub.
Overview
FGF5Gene function
What if the gene works
The FGF5 gene helps control the hair growth cycle. Its protein signals hair follicles to stop active growth and move into a resting phase, which helps set normal hair length.
Risk
What if the gene does not work
Variants in the FGF5 gene can lengthen the hair growth phase, causing unusually long scalp hair, long eyelashes, or excess body hair. Milder to more severe variants may change when this appears and how marked the hair growth is.
Treatment
What does that mean for your treatment
For a pathogenic or loss-of-function variant in the FGF5 gene, no gene-specific treatment or drug choice is currently established. The FGF5 gene is being studied as a regulator of hair growth, and FGF5-blocking approaches are under investigation in hair-loss research.
Conditions associated with FGF5
Gene function
What if the gene works
Hair growth depends on careful timing, not just how fast hair is made. The FGF5 gene provides one of the signals that tells hair follicles when active growth should wind down. This is a key part of how the FGF5 gene affects hair growth and natural hair length.
One of the main jobs of the FGF5 gene is to signal that active hair growth should begin winding down. This helps each follicle move to the next step of its normal cycle at the right time.
By setting the end point of the growing phase, this gene helps shape how long hair can grow under usual conditions. It works as a timing cue rather than as the material that builds the hair strand.
Cells release the FGF5 protein so nearby cells can receive and act on the message. In hair follicles, this local signaling helps coordinate a smooth shift from growth to the next phase.
What is a variant?
A genetic variant is a small difference in the DNA sequence of a gene. These changes are common and help account for normal human diversity, including differences in appearance, metabolism, and how the body responds to environmental influences. Many variants do not have any noticeable effect and are simply part of natural genetic variation. In some cases, though, a variant can change how a gene functions more substantially and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the FGF5 gene often weaken or shut down the protein signal that helps hair follicles switch out of the active growth phase. Changes in the FGF5 gene can affect hair growth by reducing protein stability, blocking release from the cell, or lowering how well it binds its partner receptor. Milder variants may only partly reduce signaling, while more disruptive variants can remove it almost completely and are more often linked to longer scalp hair or unusually long eyelashes.
How variants are linked to conditions
Pathogenic variants in the FGF5 gene are linked to inherited hair growth conditions. The best established association is familial trichomegaly, which can cause very long eyelashes and, in some people, longer scalp or body hair. Some families are described as having hypertrichosis because hair growth is increased in several areas. This is how variants in the FGF5 gene are linked to conditions: certain rare variants can directly cause a distinctive pattern of excess hair growth.
A variant is not necessarily a diagnosis
Genetic variants are a routine part of human biology and are widely present in the general population. Most do not have a direct effect on health and instead reflect the natural range of human diversity. For many genes, carrying a variant associated with a condition indicates a possible link rather than a definite diagnosis, especially when multiple genes and environmental factors play a role. In some situations, however, a single well characterized variant in a specific gene is enough to confirm a diagnosis.
Are there things that can increase or change my risk?
There is not yet broadly confirmed evidence on specific factors that increase or reduce health risk related to the FGF5 gene. Changes in FGF5 are best known for affecting hair growth patterns, and overall hair traits are also shaped by many other genes, hormones, age, and health factors.
Inheritance of FGF5 variants
For people reading about the FGF5 gene inheritance pattern, the well-established inherited condition linked to FGF5 follows an autosomal recessive pattern. This means a child usually inherits one FGF5 gene variant from each parent, and the parents are typically healthy carriers. When both parents carry a variant, each pregnancy has a 25% chance of the child inheriting both changed copies, a 50% chance of being a carrier, and a 25% chance of inheriting neither variant. Sons and daughters are affected equally.
What does my FGF5 result mean for my family?
FGF5 changes are best known in a rare inherited hair-growth condition, often with unusually long scalp hair or eyelashes. In families where a disease-causing FGF5 change is confirmed, close relatives may also carry the same change, and brothers, sisters, or future children could share the trait depending on the family pattern. The exact meaning for relatives depends on the specific FGF5 result and the condition linked to it.
Genetic information
Genetic testing
How you find out about variants
FGF5 genetic testing usually uses saliva, blood, or a cheek swab to look for variants in the FGF5 gene. Results can show whether a variant is present, absent, or uncertain in meaning, and they are often reviewed alongside personal or family history.
When should I consider getting a genetic test?
There is not yet a broadly established medical reason to test the FGF5 gene on its own. Decisions about genetic testing are usually based on your personal health history, family history, and the broader question your doctor or genetic counselor is trying to answer.
A genetic result is only one part of your health story
Genetic results can be very informative, yet what they can tell you varies with the condition and the kind of variant found. Over time, how the body functions is also shaped by factors like age, environment, lifestyle, and medical history. In some conditions, particularly those affected by many genes, genetic information offers context rather than certainty and makes the most sense when considered with other parts of care. In other situations, a genetic result can give a clear answer. In areas like medication response, these results may also help put individual experiences into context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how your body responds to medicines. Some people break down a drug faster or slower than others, which can change how much of the medicine reaches the body and how long it stays active. This common part of human biology can influence how well a treatment works or how sensitive someone is to side effects.
What is Pharmacogenetics?
Pharmacogenetics examines how genetic differences can affect a person’s response to medications. It looks at connections between genes and drugs to help explain why the same treatment may work differently from one person to another. For many medicines, genes influence either how strong a drug’s effects are or how the body handles it. This information can support more informed and individualized treatment decisions. More detail on this topic is available in the LearnHub.
Drugs influenced by the FGF5 gene
When should I seek medical advice?
There isn’t yet a broadly confirmed role for this gene in guiding medication choice or response, so any questions about medicines, side effects, or changes in treatment are best discussed with your doctor.
History
Long before genes were identified, breeders noticed that some animals consistently grew longer hair than others. In the 1990s, researchers linked this pattern to the FGF5 gene through studies of long-haired mice, especially the well-known angora mouse. From these first observations, research expanded steadily. Scientists later found that changes in the FGF5 gene were also tied to hair length in cats, dogs, rabbits, and several other mammals. That made FGF5 an important gene in the study of visible inherited traits, because it helped connect everyday appearance with a specific stretch of DNA. Over time, this work turned FGF5 into one of the clearest examples of how a single gene can influence hair growth across species.