The HSD17B4 gene gives your cells instructions to break down certain fats inside peroxisomes, small parts of the cell that help manage fats and related chemicals. This gene helps your body process very long chain fatty acids and some bile acid building blocks. If the gene does not work properly in both copies, these substances can build up and cause D-bifunctional protein deficiency, a rare condition linked to low muscle tone, feeding problems, seizures, hearing or vision loss, and delayed development. HSD17B4 is mainly known in rare disease genetics rather than popular culture.
What is a gene?
Genes are stretches of DNA that give your cells instructions for making molecules or guiding processes throughout the body. Some genes carry the directions for producing proteins, which are the working parts of cells. Others mainly help regulate when certain processes happen, where they happen, and how active they are. Taken together, genes affect how the body grows and works, and they can influence how you respond to food, stress, and medications. For a deeper look at this topic, you can find more in the LearnHub.
Overview
HSD17B4Gene function
What if the gene works
The HSD17B4 gene helps cells break down certain fats inside peroxisomes, small parts of the cell that process fatty acids. This supports energy balance and helps the body handle very long chain fats and some bile acid building blocks.
Risk
What if the gene does not work
More disruptive variants in the HSD17B4 gene can cause D-bifunctional protein deficiency, often with early low muscle tone, seizures, vision or hearing loss, and developmental delay. Milder variants may lead mainly to hearing loss and, in some females, ovarian insufficiency.
Treatment
What does that mean for your treatment
No treatment or drug choice is currently guided specifically by a pathogenic variant in the HSD17B4 gene; care is supportive and based on the person’s symptoms. The HSD17B4 gene is also being studied as a biomarker and possible drug target in some cancers, but that research has not led to guideline-based treatment use.
Conditions associated with HSD17B4
Gene function
What if the gene works
Your cells rely on the HSD17B4 gene to handle certain fats that need extra processing. Its protein works inside peroxisomes, small compartments that break down fatty substances. Understanding what the HSD17B4 gene does in the body helps explain how cells manage everyday fat cleanup and recycling.
The HSD17B4 gene helps carry out key middle steps in breaking down very long chain fats. This happens in peroxisomes, where fats that are too long for other cell systems are first trimmed down.
Its protein also helps process branched fats, which have side branches that make them harder for cells to handle. This keeps unusual fats from food and normal body processes moving through routine cell cleanup.
The HSD17B4 gene also helps process early bile acid building blocks made from cholesterol. These steps support the normal production of bile acids, which help your body digest and absorb fats.
What is a variant?
A genetic variant is a minor change in the DNA sequence of a gene. These changes are common and help shape normal differences between people, including 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. Sometimes, though, a variant changes how a gene works more substantially and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the HSD17B4 gene can make the protein unstable, weaken one or both of its enzyme activities, or prevent it from reaching the peroxisome, the cell compartment where it works. This is how HSD17B4 gene variants affect protein function and can lead to a buildup of very long chain fatty acids and related molecules. Some changes are milder and leave partial activity, while more severe variants often remove most function and are linked to earlier and more pronounced D-bifunctional protein deficiency.
How variants are linked to conditions
Pathogenic variants in the HSD17B4 gene cause D-bifunctional protein deficiency, a rare inherited condition that often begins in infancy and can affect development, muscle tone, vision, hearing, and the liver. Different pathogenic variants in the HSD17B4 gene can also cause Perrault syndrome, which typically includes hearing loss and, in people with ovaries, reduced ovarian function. This summary of HSD17B4 gene variants and related conditions focuses on these established associations.
A variant is not necessarily a diagnosis
Genetic variants are a usual part of human biology and are common across the general population. Most do not have a direct effect on health and simply reflect natural human diversity. For many genes, carrying a variant associated with a condition suggests a possible link rather than a definite diagnosis, especially when several genes and environmental factors are involved. In some situations, though, 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?
For HSD17B4-related disease, risk is mainly set by inheritance. A child’s chance is higher when both parents carry a harmful HSD17B4 variant, and family history can point to a higher chance. There is not enough evidence that diet, exercise, or other lifestyle changes lower this genetic risk.
Inheritance of HSD17B4 variants
HSD17B4-related conditions are inherited in an autosomal recessive pattern. This means a child usually inherits one HSD17B4 variant from each parent, and both parents are typically healthy carriers. When both parents carry a variant in the HSD17B4 gene, each pregnancy has a 25% chance of resulting in a child with the condition, a 50% chance of a child being a carrier, and a 25% chance of a child inheriting neither variant. For families asking how HSD17B4 is inherited, this pattern affects sons and daughters equally.
What does my HSD17B4 result mean for my family?
For families with an HSD17B4-related condition, close relatives may also carry the gene change, even if they feel well. Brothers and sisters may be affected or may be carriers, and parents are usually carriers. Family members may want to learn whether the same change is present, especially when planning a pregnancy.
Genetic information
Genetic testing
How you find out about variants
Genetic testing for variants in the HSD17B4 gene uses a blood or saliva sample to read the gene's DNA code. It may be done as a single-gene test or as part of a broader panel or exome test. Results can show whether you carry one or two variants, which can help confirm a diagnosis or carrier status.
When should I consider getting a genetic test?
Genetic testing for the HSD17B4 gene can be worth considering when a baby or child has signs of a rare inherited condition affecting the brain, nerves, liver, hearing, or vision, especially with delayed development or seizures. It may also help if there is a known HSD17B4 change in the family or a close relative with this condition.
A genetic result is only one part of your health story
Genetic results can be informative, but how much they reveal varies based on the condition and the kind of variant involved. Over time, the way the body works is also shaped by factors such as lifestyle, environment, age, and medical history. In some conditions, especially those influenced by many genes, genetic information provides context rather than certainty and is most useful when considered alongside other parts of care. In other situations, a genetic result may offer a clear answer. When it comes to 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 some medicines. Small differences in genes can change how quickly a drug is broken down, how much of it reaches its target, or how sensitive your body is to its effects. This helps explain why the same treatment works well for one person, works less well for another, or causes more side effects in someone else. These differences are common and are one part of the bigger picture alongside age, overall health, and other medicines.
What is Pharmacogenetics?
Pharmacogenetics is the study of how genetic differences affect the way people respond to medications. It examines the relationship between genes and drugs to help explain why a 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 handles it. This information can support more informed, individualized treatment decisions. More detail on this topic is available in the LearnHub.
Drugs influenced by the HSD17B4 gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding medication response, so general questions about medicines and side effects are best discussed with your doctor. It is a good idea to seek medical advice if a treatment causes unusual symptoms, does not seem to be helping, or you have concerns before starting a new medicine.
History
The HSD17B4 gene entered medical genetics through work on rare inherited conditions linked to peroxisomes, small parts of cells that help process certain fats. In the 1990s, researchers connected changes in this gene with D bifunctional protein deficiency, which helped clarify why some babies had a similar pattern of early neurologic and metabolic findings. From these first observations, research expanded steadily. Scientists then identified different kinds of HSD17B4 variants and showed that they could be tied to a range of disease severity. This work became an important step in the broader history of diagnosing peroxisomal conditions and understanding how gene testing could sort conditions that once looked very similar.