The HADHB gene helps your body turn certain long-chain fats into energy, especially for the heart, muscles, and liver during fasting or illness. The protein made by this gene helps your cells keep energy production steady when glucose is low. If both copies do not work properly, a person can develop an inherited fatty acid oxidation condition that may cause low blood sugar, weakness, liver or heart problems, nerve symptoms, and eye changes.
What is a gene?
A gene is a section of DNA that carries instructions your cells use to make molecules or regulate activities in the body. Some genes hold the information needed to produce proteins, the parts of cells that do much of the work. Others mainly control when certain processes take place, where they happen, and how strongly they run. Together, genes affect how the body develops and functions, and they can influence how you respond to food, stress, and medications. For a more detailed explanation, you can find more in the LearnHub.
Overview
HADHBGene function
What if the gene works
The HADHB gene helps your body break down certain long chain fats in mitochondria, the cell’s energy centers. This supports energy production, especially during fasting, exercise, and longer gaps between meals.
Risk
What if the gene does not work
Variants in the HADHB gene can impair long-chain fat breakdown, causing a fatty acid oxidation condition with low blood sugar, liver or heart problems in infancy, or later muscle pain and weakness. Milder variants may cause later, less severe symptoms.
Treatment
What does that mean for your treatment
Pathogenic variants in the HADHB gene usually guide care toward careful avoidance of fasting and a diet that limits long chain fats. Many people also use medium chain triglycerides, and some may be treated with triheptanoin. During illness or surgery, extra glucose and close monitoring can help reduce metabolic stress.
Conditions associated with HADHB
Gene function
What if the gene works
Your cells use the HADHB gene to turn long-chain fats into usable energy. It works inside mitochondria, the parts of cells that make most of the cell’s fuel. This role is especially helpful between meals, during sleep, and during longer periods of activity.
Inside mitochondria, the HADHB protein helps split long-chain fats into smaller pieces. This is one of the main ways the HADHB gene helps break down long-chain fats for energy.
The products of this step are used to make ATP (the cell’s main energy source). This helps your body keep energy flowing when it is relying more on fat, such as overnight or during exercise.
The HADHB protein works closely with the HADHA protein in a larger team that handles fats. Together, they carry out linked steps in the right order so long-chain fats can be used efficiently.
What is a variant?
A genetic variant is a small difference in the DNA sequence within a gene. These differences are common and are part of normal human diversity, including variation in appearance, metabolism, and how the body responds to environmental influences. Many variants do not have any noticeable effect and simply represent natural genetic variation. In some cases, though, a variant can change 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 HADHB gene can change the shape or stability of its protein, so cells break down long chain fats less effectively in mitochondria, the cell's energy centers. In people looking into how HADHB gene variants affect function, milder changes may leave some enzyme activity, while more disruptive variants can greatly reduce activity or prevent the protein from joining its partner correctly. This functional range often influences how early mitochondrial trifunctional protein deficiency appears and how severe it becomes.
How variants are linked to conditions
Among the health conditions linked to HADHB gene variants, the main one is mitochondrial trifunctional protein deficiency. Pathogenic variants in the HADHB gene can cause this inherited condition, which may show up in infancy, childhood, or later life with episodes of low blood sugar, liver or heart problems, muscle pain or breakdown, and nerve symptoms. In some people, the diagnosis is described more specifically as long-chain 3-ketoacyl-CoA thiolase deficiency.
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 directly affect health and instead reflect natural human diversity. For many genes, having a variant associated with a condition suggests a possible link rather than a definite diagnosis, especially when multiple genes and environmental factors play a role. 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 HADHB, risk is mainly shaped by inheritance: the condition usually happens when a child inherits a changed copy from both parents. In people living with HADHB-related fatty acid oxidation conditions, long fasting, illness, and heavy exercise can trigger dangerous low blood sugar and energy crises. Early monitoring and avoiding fasting help reduce complications.
Inheritance of HADHB variants
HADHB-related conditions are inherited in an autosomal recessive pattern, which means a child usually needs to inherit one HADHB variant from each parent to be affected. Parents who each carry one variant are often unaffected themselves, but with each pregnancy there is a 25% chance the child will inherit both variants, a 50% chance the child will be a carrier, and a 25% chance the child will inherit neither variant. In practical terms, how HADHB variants are inherited is usually the same for sons and daughters because the HADHB gene is on chromosome 2, not on a sex chromosome.
What does my HADHB result mean for my family?
For families of someone with a disease-causing HADHB result, parents are often healthy carriers, and brothers or sisters may also be affected or be carriers. Other close relatives, such as aunts, uncles, and cousins, may also carry the changed gene in the family. This can be especially relevant when planning a pregnancy, because two carriers can have a child with the condition.
Genetic information
Genetic testing
How you find out about variants
To find out whether you carry variants in the HADHB gene, genetic testing for HADHB variants analyzes DNA from a blood sample, cheek swab, or saliva sample. A lab reads the gene’s sequence and compares it with the usual pattern to identify changes that may help confirm or rule out a genetic diagnosis.
When should I consider getting a genetic test?
Consider HADHB testing if you or your child has a positive newborn screen or signs of a problem using fat for energy, such as low blood sugar during fasting or illness, muscle breakdown, heart problems, or liver trouble. It can also be helpful if a close relative has a HADHB-related condition or a known HADHB gene change, including when planning a pregnancy.
A genetic result is only one part of your health story
Genetic test results can provide meaningful information, but how much they reveal depends on the condition and the kind of variant involved. Many factors, including lifestyle, environment, age, and medical history, shape how the body functions over time. In some conditions, especially those influenced by many genes, genetic information offers context rather than certainty and is best understood 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 people respond to medicines. Two people can take the same treatment and have different results because their bodies may absorb, break down, move, or respond to a drug in different ways. This kind of variation is common and can influence how well a medicine works or how sensitive someone is to side effects.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in genes affect the way a person responds to medications. It looks at relationships 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 strongly a drug works or how the body handles it. This information can support treatment choices that are more informed and more individualized. To explore this subject in greater detail, you can read more in the LearnHub.
Drugs influenced by the HADHB gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding how medicines are chosen or used, so general questions about side effects, new symptoms, or medication changes are best discussed with your doctor.