The POLH gene gives cells instructions for a DNA copying protein that can work past UV damage from sunlight. The protein made by this gene helps your cells keep dividing after everyday sun exposure with fewer copying mistakes. If both copies of the gene do not work properly, a person can develop a form of xeroderma pigmentosum called the variant type, with marked sun sensitivity and a higher chance of skin cancers. POLH is mainly known in medical genetics rather than popular culture.
What is a gene?
Genes are stretches of DNA that provide cells with instructions to make molecules or regulate activities in the body. Some genes hold the directions for producing proteins, the parts of cells that carry out much of their work. Other genes mainly control when certain processes happen, where they happen, and how strongly they take place. Together, genes affect how the body develops and functions, and they can influence how you respond to food, stress, or medications. To explore this subject in more detail, you can find more in the LearnHub.
Overview
POLHGene function
What if the gene works
The POLH gene helps cells copy DNA when sunlight has caused small areas of damage. Its protein lets DNA copying continue past this damage, which supports skin cell repair and lowers the chance of copying mistakes.
Risk
What if the gene does not work
Changes in the POLH gene can cause xeroderma pigmentosum variant, with unusual sun sensitivity and a higher chance of skin cancers. Milder or more severe variants can affect when signs begin and how marked they are.
Treatment
What does that mean for your treatment
No POLH-specific treatment or drug selection approach is currently established. In practice, care relies on standard xeroderma pigmentosum management, such as strict UV protection and regular skin checks, rather than a medicine chosen because of the POLH gene. The POLH gene is being studied as a possible biomarker of response to some DNA damaging cancer treatments, but this is not part of routine care.
Conditions associated with POLH
Gene function
What if the gene works
Every day, sunlight and normal cell activity leave small marks on DNA. The POLH gene helps your cells keep copying DNA when they meet some of these damaged spots. Its protein is a specialized DNA copying enzyme that is especially good at working across ultraviolet, or UV, damage.
The POLH gene makes a DNA copying protein that can move past certain damaged parts of DNA. It is especially skilled at reading through UV related damage, which helps copying continue.
When the usual DNA copying machinery pauses at a damaged spot, POLH can step in as a backup. This helps the cell finish copying its DNA in a more controlled way.
POLH is better than many backup DNA copiers at placing the right DNA letters across common sun damage. Understanding what the POLH gene does is easier if you picture it helping cells copy through a roadblock caused by UV light.
What is a variant?
A genetic variant is a minor change in a gene’s DNA sequence. These changes are common and are part of normal human diversity, including differences in appearance, metabolism, and the way the body responds to environmental influences. Many variants do not have any noticeable effect and simply represent natural genetic variation. Sometimes, though, a variant changes how a gene works more significantly and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
To understand how variants influence the POLH gene's function, it helps to know that some changes make its DNA copying protein shorter, unstable, or unable to work around UV-damaged DNA. Milder variants may leave some activity, while more severe variants can sharply reduce or stop the protein's activity altogether. In xeroderma pigmentosum variant type, less remaining activity is often linked to earlier or more pronounced sun-related skin changes.
How variants are linked to conditions
Pathogenic variants in the POLH gene cause xeroderma pigmentosum, variant type, a rare inherited condition marked by extreme sensitivity to sunlight and a much higher chance of skin cancers, often starting at a young age. In families affected by POLH gene variants, symptoms can include severe sunburns, freckling in sun exposed skin, and eye irritation from light. This is a confirmed genetic diagnosis when disease causing variants are found in both copies of the gene.
A variant is not necessarily a diagnosis
Genetic variants are a routine part of being human and are widely seen across the general population. Most do not directly affect health and simply reflect normal human diversity. For many genes, having a variant associated with a condition points to a possible link rather than a certain diagnosis, particularly when several genes and environmental factors also play a role. In some situations, though, one well understood variant in a particular gene is enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For people with harmful POLH changes causing xeroderma pigmentosum variant, ultraviolet light from the sun and tanning beds can greatly raise the chance of skin damage and skin cancer. Risk is driven mainly by the gene change, so the most effective steps are strict sun protection, avoiding UV exposure, and regular skin checks to catch problems early.
Inheritance of POLH variants
For families asking how POLH gene variants are inherited, the usual pattern is autosomal recessive. This means a person typically inherits one altered copy of the POLH gene from each parent. Parents who each carry one variant usually do not have the condition themselves, but with each pregnancy they have a 25% chance of having a child with POLH-related xeroderma pigmentosum variant type, a 50% chance of having a child who is a carrier, and a 25% chance of having a child with two working copies. Sons and daughters are affected at the same rate.
What does my POLH result mean for my family?
For POLH, family members are usually affected only if they inherited a changed copy from each parent. Brothers and sisters may also have the condition or be carriers, and parents are often carriers without symptoms themselves. Other relatives, such as aunts, uncles, and cousins, may also carry the family’s POLH change.
Genetic information
Genetic testing
How you find out about variants
To find out whether you carry a variant, POLH genetic testing uses a blood or saliva sample to read the POLH gene. This is how POLH genetic testing works: a lab checks the DNA sequence for changes and compares them with known patterns. Results may show no variant, a benign variant, or a variant linked to disease.
When should I consider getting a genetic test?
Consider genetic testing for the POLH gene if someone has a rare condition where skin cannot properly handle sunlight, often causing marked sun sensitivity, heavy freckling in childhood, or skin cancers at a young age; this is known medically as xeroderma pigmentosum variant. Testing can also help when a close relative has this condition or a known POLH gene change.
A genetic result is only one part of your health story
A genetic result can provide useful insight, but how much it explains depends on the condition and the kind of variant involved. Over time, many factors, including lifestyle, environment, age, and medical history, influence how the body works. In some conditions, especially those shaped by many genes, genetic information offers context rather than certainty and is best considered alongside other parts of care. In other situations, a genetic result may give a clear answer. In areas such as medication response, genetic results can 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. This helps explain why the same treatment works well for one person, has less effect in another, or causes more side effects in someone else. Small differences in genes can change how the body breaks down a drug, moves it through the body, or responds to it at its target. These differences are common and are one reason medication response can vary from person to person.
What is Pharmacogenetics?
Pharmacogenetics looks at how differences in genes can affect the way someone responds to medication. It examines links between genes and drugs to help explain why the same treatment may work differently from one person to another. For many medicines, genes can influence how strong a drug’s effects are or how the body processes it. This understanding can support more informed, personalized treatment decisions. More detail on this topic is available in the LearnHub.
Drugs influenced by the POLH gene
When should I seek medical advice?
This gene does not currently have a broadly confirmed role in guiding medication response, so concerns about side effects, treatment changes, or how medicines may affect you are best discussed with your doctor.
History
Throughout history, doctors described people with extreme sensitivity to sunlight, and by the 20th century some cases were recognized as a distinct form of xeroderma pigmentosum called the variant type. Unlike the more familiar forms, these families did not show the usual DNA repair problem, which puzzled researchers for years. From these first observations, research expanded steadily. In 1999, scientists identified the POLH gene as the cause of xeroderma pigmentosum variant, linking the condition to a different way cells cope with ultraviolet light. That finding helped explain why people with this type could have similar skin cancer risk but a different lab pattern. The POLH gene became an important milestone in understanding how inherited cancer risk can arise through more than one biological pathway.