The MSH6 gene helps repair small mistakes that happen when cells copy DNA. If it is not working properly, these errors can build up, which can cause Lynch syndrome and increase the chance of cancers such as colorectal and endometrial cancer. The protein made by this gene helps your cells keep genetic instructions accurate over time.
What is a gene?
Genes are sections of DNA that carry instructions your cells use to make molecules or direct processes throughout the body. Some genes provide the code for proteins, which are the parts of cells that do the work. Others mainly regulate when certain processes happen, where they take place, and how active they are. Taken together, genes affect how the body grows and works, and they can also influence how you respond to food, stress, and medicines. More detailed information on this topic is available in the LearnHub.
Overview
MSH6Gene function
What if the gene works
The MSH6 gene helps cells find and repair small DNA copying mistakes. This supports healthy cell growth and helps keep genetic information stable over time.
Risk
What if the gene does not work
Variants in the MSH6 gene can cause Lynch syndrome, raising colorectal and uterine cancer risk. Milder or more severe variants may affect when cancer appears; two nonworking copies cause a rare childhood condition with high cancer risk and developmental differences.
Treatment
What does that mean for your treatment
No treatment is chosen solely because of a pathogenic variant in the MSH6 gene. In practice, drug choices are guided by whether the tumor shows mismatch repair deficiency (trouble fixing DNA copying errors) or microsatellite instability (a related pattern of DNA change), often linked to loss of MSH6. When that pattern is present, immune checkpoint inhibitors such as pembrolizumab or dostarlimab can be appropriate options.
Conditions associated with MSH6
Gene function
What if the gene works
Every time a cell divides, it needs to copy a huge amount of DNA with care. The MSH6 gene helps your body check that fresh copy and correct small errors. This steady proofreading supports healthy cell turnover in places like the gut, skin, and blood.
The MSH6 gene helps cells notice small DNA copying mistakes soon after the DNA is made. It is especially good at finding mismatched DNA letters and tiny stretches where a letter was added or missed.
After an error is found, this gene’s protein works with partner proteins to start DNA mismatch repair, the system that fixes copy errors. It helps direct the cell to remove the wrong section and rebuild it using the correct template.
By correcting routine copy errors, the MSH6 gene helps keep genetic information steady from one cell generation to the next. This supports normal growth, tissue renewal, and other everyday processes that depend on accurate DNA.
What is a variant?
A genetic variant is a small difference in a gene’s DNA sequence. These changes are common and are part of normal human diversity, including differences in appearance, metabolism, and how the body responds to environmental influences. Many variants do not cause any noticeable effect and simply represent natural genetic variation. In some cases, however, 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
In the MSH6 gene, variants can alter the protein's shape, shorten it, or interfere with how the cell reads the gene, so DNA copy errors are fixed less well. Some variants only partly reduce repair activity, while more disruptive variants can leave little or no working protein. This helps explain how variants in the MSH6 gene affect DNA repair and why stronger loss of function is linked to Lynch syndrome cancers, while milder changes may have a smaller effect.
How variants are linked to conditions
Pathogenic variants in the MSH6 gene are a well-established cause of Lynch syndrome, an inherited condition linked to higher lifetime risk of colorectal, endometrial, ovarian, stomach, urinary tract, and some other cancers. When a person carries two pathogenic variants in the MSH6 gene, this can cause constitutional mismatch repair deficiency, a rare condition associated with childhood cancers and other features.
A variant is not necessarily a diagnosis
Genetic variants are a normal feature of human biology and are common throughout the general population. Most have no direct impact on health and simply represent natural human diversity. For many genes, carrying a variant associated with a condition indicates a possible link rather than a definite diagnosis, especially when more than one gene and environmental factors play a role. In some situations, though, a single well-characterized variant in a specific gene can be enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For MSH6, cancer risk is mostly driven by the inherited variant itself. Risk also changes with age, sex, and family history, and some cancers are more common in women living with MSH6. Screening does not change the gene-related risk, but it can help find cancer early or prevent some cancers, especially colon cancer.
Inheritance of MSH6 variants
Inheritance of the MSH6 gene variants depends on the condition involved. A single pathogenic variant in the MSH6 gene is usually inherited in an autosomal dominant pattern, as seen in Lynch syndrome, so each child of a parent who carries it has a 50% chance of inheriting that variant. When a person inherits pathogenic variants in both copies of the MSH6 gene, one from each parent, it can cause a separate condition called constitutional mismatch repair deficiency, which follows an autosomal recessive pattern. This means parents can be healthy carriers while a child inherits both altered copies.
What does my MSH6 result mean for my family?
For many living with an MSH6 change linked to Lynch syndrome, close relatives such as parents, brothers, sisters, and children may also carry the same change, so the result can matter across the family. MSH6 can also be linked to a rarer childhood condition when a child inherits changed copies from both parents, so family meaning depends on which MSH6-related condition applies to the result.
Genetic information
Genetic testing
How you find out about variants
MSH6 genetic testing for Lynch syndrome usually uses a blood or saliva sample. A lab reads your DNA to look for inherited variants, and the report may show a benign variant, a variant of uncertain significance, or a pathogenic variant that can confirm an inherited cancer predisposition.
When should I consider getting a genetic test?
Consider testing for the MSH6 gene if you or close relatives have had colon cancer or cancer of the womb lining, especially at a younger age, or several related cancers in one family. Testing may also be considered when a tumor shows signs that the body’s DNA repair system is not working normally.
A genetic result is only one part of your health story
A genetic result can provide useful insight, but how much it reveals depends on the condition and the specific type of variant involved. Many factors, including lifestyle, environment, age, and medical history, shape how the body functions over time. For some conditions, especially those influenced by many genes, genetic information offers context rather than certainty and is best understood together with 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 people respond to medicines. This helps explain why the same treatment works well for one person, does very little for another, or causes more side effects in someone else. Small differences in how the body breaks down, moves, or responds to a drug are common, and they can influence how strongly a medicine works or how sensitive a person is to it.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in a person’s genes affect their response to medications. It studies relationships between genes and drugs to better understand why the same treatment can work differently from one person to another. For many medicines, genes can influence both how strongly a drug works and how the body processes it. This information can support more informed, individualized treatment decisions. More detailed information on this topic is available in the LearnHub.
Drugs influenced by the MSH6 gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in predicting medication response, so general questions about medicines or side effects are best discussed with your doctor or pharmacist.
History
The MSH6 gene entered medicine through research on families with Lynch syndrome, an inherited condition linked to a higher chance of certain cancers. In the 1990s, scientists identified MSH6 as one of the key genes behind this pattern, adding to earlier work on the body’s DNA mismatch repair system, which fixes copying errors in DNA. From these first observations, research expanded steadily. Doctors then recognized that variants in the MSH6 gene could be associated with a somewhat different cancer pattern than some other Lynch syndrome genes, often with later onset and a wider age range at diagnosis. Scientific classifications changed as researchers learned more about the gene. That history helped shape today’s use of genetic testing for inherited cancer risk.