The PHGDH gene gives your body instructions for making serine, a building block that supports brain growth, nerve function, and many everyday cell tasks. This gene plays an important role in the pathway that lets cells make serine when diet alone is not enough. If the PHGDH gene is not working properly, some people develop PHGDH deficiency, which can lead to a smaller than expected head size, seizures, developmental delay, and other brain and nerve problems. PHGDH is mainly known in medical genetics rather than popular culture.
What is a gene?
Genes are sections of DNA that give your cells information they can use to make molecules or regulate processes in the body. Some genes carry the instructions for producing proteins, the parts of cells that do the work. Others mainly help direct when certain processes happen, where they occur, and how strongly they run. As a group, genes affect how the body develops and works, and they can also shape how you respond to food, stress, or medications. For a deeper look at this subject, you can find more in LearnHub.
Overview
PHGDHGene function
What if the gene works
The PHGDH gene helps cells make serine, a building block used to make proteins, fats in cell membranes, and DNA. This supports normal growth, brain development, and everyday cell function.
Risk
What if the gene does not work
Pathogenic variants in the PHGDH gene can cause serine deficiency conditions that affect brain development, often with small head size, seizures, and developmental delay. Milder variants may cause less severe features, while severe variants can cause Neu-Laxova syndrome before birth.
Treatment
What does that mean for your treatment
Pathogenic variants in the PHGDH gene can make L-serine treatment, often with added glycine, a central part of care. Starting therapy early may help reduce seizures and support development. No drug choice based on the PHGDH gene beyond this amino acid replacement approach is currently established.
Conditions associated with PHGDH
Gene function
What if the gene works
Your cells use the PHGDH gene to start making serine, a small amino acid used every day. This pathway helps cells keep a steady supply of basic materials for growth, repair, and routine upkeep. Understanding how the PHGDH gene works in the body helps explain how cells connect energy use with making their own building blocks.
Its protein starts the main pathway for making serine inside cells. Serine is used to build proteins and support many routine cell reactions.
This pathway links part of sugar processing to serine production. It lets cells turn some everyday fuel into raw material for maintenance and growth.
Serine from this pathway helps folate carry small chemical units from one reaction to another. That supports the making of DNA building blocks and other compounds cells use as they grow and renew themselves.
What is a variant?
A genetic variant is a small difference in the DNA sequence within a gene. These changes are common and help shape normal human diversity, such as differences in appearance, metabolism, or the way the body responds to environmental influences. Many variants do not have any noticeable effect and simply represent natural genetic variation. In some situations, 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
Many variants in the PHGDH gene lower how well cells make the PHGDH enzyme or change its shape, so its activity drops and serine production falls. Milder variants may leave some enzyme activity, while more severe variants can remove almost all activity or create a shortened, unstable protein. This range helps explain how PHGDH gene variants affect function and why some people have milder serine deficiency, while others develop earlier and more severe features.
How variants are linked to conditions
Pathogenic variants in the PHGDH gene can cause a rare inherited condition often called PHGDH deficiency, which may lead to small head size, developmental delay, and seizures. More disruptive biallelic variants can also cause Neu-Laxova syndrome, a condition that affects growth and development before birth. Some common PHGDH gene variants linked to macular telangiectasia type 2 are associated with higher risk of this eye condition, but they do not mean someone will definitely develop it.
A variant is not necessarily a diagnosis
Variants in genes are common in the general population and are a normal feature of human biology. Most do not have a direct effect on health and simply contribute to natural human diversity. For many genes, carrying a variant associated with a condition suggests a possible link rather than a definite diagnosis, especially when multiple genes and environmental factors also play a role. In some cases, 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 PHGDH, risk is mainly shaped by inheritance rather than lifestyle. A child’s chance of having a PHGDH-related condition is higher when both parents carry a harmful PHGDH change, and this can be more likely in families with relatives who have the condition or where parents are biologically related.
Inheritance of PHGDH variants
For families learning how PHGDH gene variants are inherited, the established pattern is autosomal recessive. This means a child usually needs to inherit two disease causing PHGDH gene variants, one from each parent, to have a PHGDH-related condition. Parents who each carry one variant are typically unaffected carriers, and with each pregnancy they have a 25% chance of having an affected child, a 50% chance of having a carrier child, and a 25% chance of having a child without either variant. Sons and daughters are affected equally.
What does my PHGDH result mean for my family?
For families with a disease-causing PHGDH result linked to a recognized PHGDH-related condition, close relatives may also be carriers, even if they are healthy. Brothers and sisters could be affected or could carry the same change, and relatives planning children may want to know whether the variant runs in the family. The family impact depends on the exact PHGDH result and the condition it is tied to.
Genetic information
Genetic testing
How you find out about variants
PHGDH genetic testing looks for variants in the PHGDH gene using a blood sample, saliva, or cheek swab. A lab reads the gene’s DNA code and compares it with the usual sequence to see whether a variant is present, which can help show whether symptoms match a condition linked to the PHGDH gene.
When should I consider getting a genetic test?
Consider PHGDH genetic testing if a child has signs of a rare inherited condition that affects brain development, such as a very small head size, developmental delay, or hard-to-control seizures, especially when symptoms start early. Testing can also help when there is a known family history of a PHGDH change.
A genetic result is only one part of your health story
Genetic test results can provide useful insight, but how much they reveal varies by the condition and the kind of variant involved. How the body works over time is also shaped by many factors, including lifestyle, environment, age, and medical history. For some conditions, especially those influenced by many genes, genetic information adds context rather than certainty and is best understood together with other parts of care. In other situations, a genetic result may offer a clear answer. In areas like medication response, genetic results can also help put individual experiences into perspective.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how your body responds to medicines. Some people break down a drug more slowly or more quickly, while others may be more or less sensitive to its effects. This helps explain why the same treatment can work well for one person, seem less effective for another, or cause more side effects in someone else.
What is Pharmacogenetics?
Pharmacogenetics examines how genetic differences affect the way people respond to medications. It studies gene and drug patterns to help explain why the same treatment may work differently from one person to another. For many medicines, genes can influence both how the body processes a drug and how strong its effects are. This information can support more informed and more individualized treatment decisions. If you want to read more about this topic, you can learn more in the LearnHub.
Drugs influenced by the PHGDH gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding routine medication decisions, so general health or medicine concerns are best discussed with your doctor. PHGDH is being studied in some cancer research as a possible treatment target, but this is not part of standard prescribing in everyday care.
History
PHGDH first drew scientific attention through studies of serine production in cells during the mid 20th century, before the gene itself was fully mapped. Once the PHGDH gene was identified, researchers linked inherited variants to a rare condition affecting brain development and growth, which gave the gene clearer clinical importance. From these first observations, research expanded steadily. Interest in the PHGDH gene grew again when cancer studies found that some tumors increase its activity as they adapt their metabolism. That shift moved PHGDH from a mainly biochemical topic into both medical genetics and cancer research. Over time, scientists’ understanding of the gene’s role has changed, with its history now spanning rare inherited conditions and tumor biology.