The SLC6A19 gene makes a transporter that helps the small intestine and kidneys move certain amino acids, the building blocks of protein. When it does not work well, your body absorbs less from food and loses more in urine. This gene helps your body take in tryptophan, and pathogenic variants can cause Hartnup condition, with a sun-sensitive rash, diarrhea, and episodes of poor balance or mood changes, often during illness or poor nutrition.
What is a gene?
Genes are sections of DNA that hold instructions your cells use to make molecules or regulate processes in the body. Some genes provide the information needed to produce proteins, the working parts of cells. Others mainly guide when certain processes happen, where they take place, and how active they are. Taken together, genes affect how the body develops and works, and they can influence how you respond to food, stress, and medications. For a closer look at this topic, you can learn more in the LearnHub.
Overview
SLC6A19Gene function
What if the gene works
The SLC6A19 gene helps your small intestine and kidneys move certain amino acids, the building blocks of protein. This supports normal nutrition by absorbing them from food and returning them from urine to the body.
Risk
What if the gene does not work
Variants in the SLC6A19 gene can cause Hartnup condition, which reduces absorption of certain amino acids in the gut and kidneys. Milder variants may cause few symptoms, while more severe variants can lead to rash, balance problems, or mood changes.
Treatment
What does that mean for your treatment
Pathogenic variants in the SLC6A19 gene usually shift care toward nutritional treatment rather than a gene targeted drug. Management often includes a high protein diet and nicotinamide, a form of vitamin B3, especially during symptoms or pellagra like rash. Sun protection can also help limit skin flares.
Conditions associated with SLC6A19
Gene function
What if the gene works
Your body uses the SLC6A19 gene to move certain amino acids into cells in the small intestine and kidneys. This helps you absorb amino acids from food and keep them from being lost after the kidneys filter your blood. These amino acids are important building blocks for proteins and many everyday body processes.
In the small intestine, the SLC6A19 gene helps move neutral amino acids from digested food into the cells lining the gut. This is a key step in how your body absorbs amino acids from food for growth, repair, and routine body work.
In the kidneys, this gene helps reclaim neutral amino acids from the filtered fluid before they leave the body in urine. That recycling step helps your body hold on to useful nutrients instead of wasting them.
Its protein uses sodium, a natural mineral in body fluids, to help pull amino acids across the cell surface. This linked movement makes transport more efficient where the body needs to absorb or recapture these nutrients.
What is a variant?
A genetic variant is a minor difference in the DNA sequence within a gene. These changes are common and help shape normal human diversity, including differences 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 instances, though, a variant can change how a gene functions more significantly and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the SLC6A19 gene can make its amino acid transporter fold poorly, break down sooner, or fail to reach the cell surface, so neutral amino acids move into cells less well. This is how SLC6A19 gene variants affect amino acid transport. Some variants only partly reduce transport, while more severe variants can leave very little activity, which may be linked to earlier or more noticeable features of Hartnup condition.
How variants are linked to conditions
Pathogenic variants in the SLC6A19 gene cause Hartnup disorder, a rare inherited condition often identified by higher levels of certain amino acids in urine. Some people have skin rashes, balance problems, or episodes linked to low niacin, while others are only mildly affected. In medical genetics, the SLC6A19 gene and Hartnup disorder are the main well-established condition association.
A variant is not necessarily a diagnosis
Genetic variants are a routine part of human biology and are widely found in the general population. Most do not have a direct effect on health and instead represent normal 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, however, a single well-characterized variant in a particular gene can be enough to confirm a diagnosis.
Are there things that can increase or change my risk?
For people with harmful changes in both copies of the SLC6A19 gene, the chance of having Hartnup condition is mainly set by genetics. Symptoms can be more likely or more noticeable during poor nutrition, illness, stress, or heavy sun exposure. Avoiding strong sunlight and keeping up good nutrition may help lower flare-ups, but they do not change the underlying genetic condition.
Inheritance of SLC6A19 variants
Variants in the SLC6A19 gene linked to Hartnup condition are inherited in an autosomal recessive pattern. This means a child usually inherits one changed copy of the SLC6A19 gene from each parent, while parents with one changed copy are typically carriers. When both parents are carriers, each pregnancy has a 25% chance of a child inheriting both changed copies, a 50% chance of being a carrier, and a 25% chance of inheriting neither changed copy. In practical terms, the inheritance of the SLC6A19 gene variants affects sons and daughters equally, and either parent can pass the variant on.
What does my SLC6A19 result mean for my family?
For families, an SLC6A19 result is most often relevant in a recessive condition called Hartnup condition. Brothers and sisters of someone with a disease-causing result may also be affected or may be carriers, and parents are usually carriers as well. Other relatives, especially those planning children, may also want to know whether the variant runs in the family.
Genetic information
Genetic testing
How you find out about variants
Testing for SLC6A19 gene variants uses a blood or saliva sample, and a lab reads the DNA code of the SLC6A19 gene to look for changes. This kind of genetic testing can help confirm whether a person has a disease causing variant linked with Hartnup condition when symptoms and other findings fit.
When should I consider getting a genetic test?
Consider testing the SLC6A19 gene if someone has signs of Hartnup condition, such as a sun-sensitive rash, periods of poor coordination, or urine tests showing unusual amino acid loss, especially with a family history. Testing can help confirm whether SLC6A19 changes 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 varies by the condition and the kind of variant involved. Many factors, including lifestyle, environment, age, and medical history, influence how the body functions over time. For some conditions, especially those shaped by many genes, genetic information offers context rather than certainty and is best understood together with other aspects of care. In other situations, a genetic result may give a clear answer. In areas such as medication response, genetic results can also help place individual experiences in context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. Small differences in DNA can change how the body absorbs, breaks down, transports, or responds to a drug, so the same treatment may work better for one person than another. These differences are common and can influence both how well a medicine helps and how likely someone is to notice side effects.
What is Pharmacogenetics?
Pharmacogenetics examines how genetic differences shape a person’s response to medications. By looking at the relationship between genes and drugs, it helps explain why the same treatment may work differently from one person to another. For many medicines, genes influence how the body processes a drug or how strongly it works. This information can support more informed, personalized treatment decisions. To explore this topic further, you can learn more in the LearnHub.
Drugs influenced by the SLC6A19 gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding medication choice, so questions about medicines, side effects, or your overall health are best discussed with your doctor or pharmacist.
History
SLC6A19 came into medical focus through studies of Hartnup condition, first described in the 1950s in families with characteristic patterns of amino acid loss in the urine and skin or nerve related symptoms. Initially understood only through visible traits, later recognized as tied to a specific gene, it became clear that the condition reflected a problem in transporting certain amino acids. From these first observations, research expanded steadily. In the early 2000s, researchers linked Hartnup condition to variants in the SLC6A19 gene, giving a clear genetic explanation for findings doctors had tracked for decades. This discovery helped connect older clinical reports with modern genetic testing and brought greater precision to diagnosis.