The MTHFS gene helps your body use folate, a B vitamin needed to make DNA and support brain and nerve development. If this gene does not work properly, folate processing is disrupted, and some people develop MTHFS deficiency, a rare inherited condition that can affect development, movement, muscle tone, and seizure risk. Babies or children with two nonworking copies may also have feeding problems or a smaller head size.
What is a gene?
Genes are segments of DNA that carry instructions your cells use to make molecules or direct processes in the body. Some genes hold the directions for producing proteins, the parts of cells that do the work. Others mainly regulate when certain processes happen, where they occur, and how strongly they are carried out. Together, genes affect how the body develops and functions, 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
MTHFSGene function
What if the gene works
The MTHFS gene helps convert folate into active forms your cells use to make DNA and carry out other basic chemical reactions. This supports normal cell growth and development.
Risk
What if the gene does not work
More severe variants in the MTHFS gene can cause a rare condition with developmental delay, seizures, low muscle tone, and small head size. Milder variants may leave some function, which can influence when symptoms start and how marked they are.
Treatment
What does that mean for your treatment
A pathogenic or loss of function variant in the MTHFS gene does not currently direct a standard treatment or medication choice in clinical guidelines. Published reports have explored folate related treatment strategies, but these remain individualized rather than standard care.
Conditions associated with MTHFS
Gene function
What if the gene works
Your cells need the MTHFS gene to keep folate in a usable, active cycle. This supports everyday tasks such as making DNA and helping cells grow and renew. When it works properly, folate moves smoothly through this pathway instead of getting stuck in a storage form. This is an important part of normal folate metabolism.
The MTHFS gene helps change folinic acid, a stored folate form, into an active folate form your cells can use. This keeps folate available for other essential cell jobs.
Active folate from this pathway helps cells make the building blocks of DNA. That supports normal cell division, growth, and routine tissue upkeep.
Steady folate flow also supports methylation (a chemical tagging process cells use to manage many routine functions). This helps cells keep normal day to day activity across the body.
What is a variant?
A genetic variant is a minor change in the DNA sequence within a gene. 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 cause any noticeable effect and simply represent natural genetic variation. In some instances, though, a variant changes how a gene works to a greater extent and may contribute to, or directly cause, a genetic condition.
Genetic variants
What if the gene does not work
Variants in the MTHFS gene can make its enzyme unstable, weaken folate binding, or sharply reduce activity, so cells have less usable folate for DNA building and other core tasks. How MTHFS gene variants affect folate processing depends on severity: milder variants may leave some activity, while more severe variants can nearly switch the enzyme off. When very little activity remains, MTHFS deficiency often begins earlier and may be more pronounced.
How variants are linked to conditions
Rare pathogenic variants in the MTHFS gene can cause MTHFS deficiency, a rare inherited condition that affects early brain development. In reports on MTHFS gene variants and rare neurologic conditions, children with this condition may have developmental delay, intellectual disability, seizures, small head size, and changes on brain scans. A confirmed diagnosis is usually linked to pathogenic variants in both copies of the gene.
A variant is not necessarily a diagnosis
Genetic variants are common across the general population and are a normal feature of human biology. Most do not directly affect health and instead reflect the natural range of human diversity. For many genes, having a variant associated with a condition points to a possible link rather than a certain diagnosis, particularly when more than one gene and environmental influences play a part. There are cases, though, in which one well-characterized variant in a particular gene is enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For MTHFS, risk is mainly shaped by inheritance rather than lifestyle. A child is affected when both copies of the MTHFS gene are changed, so risk is higher when both parents carry a harmful variant, especially in families with a history of the condition or where parents are related by blood.
Inheritance of MTHFS variants
Variants in the MTHFS gene linked to MTHFS-related disease are inherited in an autosomal recessive pattern. This means a child usually inherits one changed copy of the MTHFS gene from each parent, and the parents are often healthy carriers. When both parents carry an MTHFS gene variant, each pregnancy has a 25% chance that the child will inherit both changed copies, a 50% chance the child will be a carrier, and a 25% chance the child will inherit neither changed copy. This inheritance pattern explains how MTHFS gene variants can run quietly through families for generations.
What does my MTHFS result mean for my family?
For families with an MTHFS-related condition, the pattern is usually recessive, which means parents are often healthy carriers. Brothers and sisters may also be carriers, and in some families a sibling may also be affected, even if symptoms differ. Close relatives may want to learn whether the family variant is present, especially when planning children.
Genetic information
Genetic testing
How you find out about variants
To find out about changes in the MTHFS gene, doctors use genetic testing for MTHFS variants, usually on blood or saliva. Sequencing reads the DNA code to look for variants in the MTHFS gene and can show whether a person has a variant in one copy or both copies. This helps clarify whether symptoms may have an inherited explanation.
When should I consider getting a genetic test?
Consider testing if a baby or child has unexplained developmental delay, seizures, low muscle tone, or other signs of a rare problem with how the body uses folate (vitamin B9), especially if there is a family history or a previous affected child. Testing can help confirm whether changes in the MTHFS gene are the cause.
A genetic result is only one part of your health story
Genetic results can provide useful insight, but how much they reveal depends on the condition and on the kind of variant involved. Over time, many factors shape how the body functions, including lifestyle, environment, age, and medical history. For some conditions, especially those influenced by many genes, genetic information offers context rather than certainty and is most helpful when considered alongside other parts of care. In other situations, a genetic result may give a clear answer. In areas like medication response, genetic results can also help place individual experiences in context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can influence how your body processes and responds to medicines. That helps explain why the same treatment may work well for one person, have less effect in another, or cause more side effects in some people. These differences are common and can affect both how well a medicine works and how sensitive your body is to it, alongside other factors such as age, liver and kidney function, and other medicines.
What is Pharmacogenetics?
Pharmacogenetics looks at how genetic variants can affect a person’s response to medications. It studies connections 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 both how strongly a drug works and how the body processes it. This information can support treatment decisions that are more informed and more individualized. You can read more about this topic in the LearnHub.
Drugs influenced by the MTHFS gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding medicine choice or dosing, so questions about side effects, treatment changes, or family health concerns are best discussed with your doctor. MTHFS has been studied in early research around antifolate medicines such as methotrexate, but this has not become a routine part of care.