The SQOR gene helps your cells break down hydrogen sulfide, a gas your body makes in small amounts, so it does not build up and interfere with energy production. This gene plays an important role in how mitochondria, the parts of cells that make energy, keep tissues working steadily. If the SQOR gene is not working properly, hydrogen sulfide can accumulate and may affect the brain, muscles, and other organs, sometimes causing episodes of weakness, low muscle tone, developmental problems, or sudden illness during stress.
What is a gene?
Genes are stretches of DNA that carry instructions your cells can use to make molecules or regulate processes in the body. Some genes provide the directions for making proteins, which are the working parts of cells. Other genes mainly help determine when, where, and how strongly certain processes take place. Together, genes affect how the body develops and works, and they can influence how you respond to food, stress, or medications. If you want to look into this topic more deeply, you can learn more in the LearnHub.
Overview
SQORGene function
What if the gene works
The SQOR gene helps your cells break down hydrogen sulfide, a gas your body makes in small amounts. Its protein works in mitochondria, helping turn this compound into safer forms while supporting normal energy production.
Risk
What if the gene does not work
More disruptive variants in the SQOR gene can cause sulfide oxidation deficiency, which may lead to episodic encephalopathy, developmental regression, low muscle tone, and characteristic brain changes, often after illness. Milder variants may cause later onset or less severe features.
Treatment
What does that mean for your treatment
No SQOR-specific treatment or drug selection approach is currently established in clinical guidelines for people with pathogenic variants in the SQOR gene. The SQOR gene is being studied in mitochondrial sulfide metabolism, and this may help future work on targeted treatments, but it has not yet changed routine care.
Gene function
What if the gene works
Your cells make small amounts of hydrogen sulfide as part of normal metabolism. The SQOR gene helps process this substance inside mitochondria, the parts of cells that help make energy. This is a key part of what the SQOR gene does in the body each day. It supports steady energy use and balanced sulfur chemistry.
The SQOR gene helps your cells start breaking down hydrogen sulfide, a natural gas your body makes in small amounts. It carries out the first step inside mitochondria, the parts of cells that support energy production.
Its protein passes electrons, tiny packets of energy, to coenzyme Q, a helper in the cell's energy system. This connects sulfide handling with routine energy production.
By clearing hydrogen sulfide in a controlled way, the SQOR gene helps keep this natural body chemical in a useful range. That balance supports normal cell signaling and how your body handles sulfur containing chemicals.
What is a variant?
A genetic variant is a small change in a gene’s DNA sequence. These changes are common and help account for normal human diversity, such as differences in appearance, metabolism, or the way the body responds to environmental influences. Many variants do not cause 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
Variants in the SQOR gene can weaken the enzyme, make it unstable, or stop cells from building it correctly in mitochondria. In simple terms, this is how SQOR gene variants affect enzyme activity: milder variants may leave some activity, while more severe variants can sharply reduce it or remove it altogether. When that happens, cells may handle hydrogen sulfide less effectively, which can disrupt mitochondrial energy balance and related cell signaling.
How variants are linked to conditions
Pathogenic variants in both copies of the SQOR gene cause sulfide quinone oxidoreductase deficiency, a rare inherited mitochondrial condition. Reported features include developmental delay or loss of skills, low muscle tone, seizures, feeding problems, and episodes of brain injury that can resemble Leigh syndrome, often during illness. This is the main well-established way SQOR gene variants are linked to conditions.
A variant is not necessarily a diagnosis
Genetic variants are a normal feature of human biology and are common throughout 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 indicates a possible link rather than a definite diagnosis, especially when more than one gene and environmental factors are involved. In some situations, though, a single well-characterized variant in a particular gene is enough to confirm a diagnosis.
Are there things that can increase or change my risk?
There is not yet broadly confirmed evidence on specific factors that increase or reduce risk related to the SQOR gene. For many families, risk is shaped mainly by whether a person inherits changed copies of SQOR from both parents, so personal questions about risk are best discussed with a doctor or genetic counselor.
Inheritance of SQOR variants
SQOR gene variants linked to SQOR related disease are inherited in an autosomal recessive pattern. This means a person usually inherits one altered copy of the SQOR gene from each parent. Parents who each carry one variant are often unaffected themselves, but with each pregnancy they have a 25% chance of having a child with the condition, a 50% chance of having a child who is a carrier, and a 25% chance of having a child with two usual copies of the gene. In short, SQOR gene inheritance typically involves two changed copies rather than one.
What does my SQOR result mean for my family?
Changes in the SQOR gene are linked to a rare inherited condition that usually affects families in a recessive way. For relatives, this often means parents can be healthy carriers, and brothers, sisters, or future children could also carry the same gene change or, in some cases, be affected. Close family members may want to learn whether the same result runs in the family.
Genetic information
Genetic testing
How you find out about variants
Genetic testing for SQOR variants usually uses a blood or saliva sample, which a lab analyzes by reading the DNA sequence in the SQOR gene. This can show whether you carry a variant and may help clarify a genetic diagnosis or explain a family pattern of similar symptoms.
When should I consider getting a genetic test?
Testing for the SQOR gene may be considered if a child has repeated episodes of severe drowsiness, seizures, breathing trouble, or sudden worsening during infections, fasting, or vomiting, especially when doctors suspect a rare inherited condition affecting the body's energy use. It can also be helpful when there is a family history of similar episodes or a known SQOR gene change.
A genetic result is only one part of your health story
Genetic test results can offer useful insight, but how much they show depends on the condition and the type of variant involved. How the body works over time is also shaped by many other 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 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 put individual experiences into context.
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 quickly or more slowly, while others may be more or less sensitive to its effects. This helps explain why the same treatment can work well for one person, have less benefit for another, or cause more side effects in someone else.
What is Pharmacogenetics?
Pharmacogenetics examines the way genetic differences shape a person’s response to medications. It studies links between genes and drugs to help explain why the same treatment can work differently in different people. With many medicines, genes can influence how powerfully a drug works or how the body handles it. This information can support treatment choices that are more informed and more tailored to the individual. To explore this subject further, you can learn more in the LearnHub.
Drugs influenced by the SQOR gene
When should I seek medical advice?
There isn't yet a broadly confirmed role for this gene in guiding how medicines are chosen or used. If you have concerns about side effects, a new medicine, or how treatment fits with your health history, talk with your doctor or pharmacist.
History
In recent decades, awareness of the SQOR gene’s role has grown. SQOR was first studied through its enzyme activity in sulfur using bacteria, where scientists saw how cells handle hydrogen sulfide. Building on this early work, researchers later identified the human SQOR gene and showed that it is active in mitochondria, the parts of cells that make energy. This linked older sulfur biology research with human metabolism. More recent medical reports connected rare, harmful variants in the SQOR gene with episodes of severe brain injury triggered by illness, especially in infancy and childhood. These findings moved SQOR from a mainly laboratory topic into clinical genetics.