Genetics and Hartnup disease

Genetic Changes

Hartnup disease is caused by mutations in the SLC6A19 gene. This gene provides instructions for making a protein called B0AT1, which is primarily found embedded in the membrane of intestine and kidney cells. The function of this protein is to transport certain amino acids into cells. In the intestines, amino acids from food are transported into intestinal cells then released into the bloodstream so the body can use them. In the kidneys, amino acids are reabsorbed into the bloodstream instead of being removed from the body in urine. In the body, these amino acids are used in the production of many other substances, including vitamins and proteins. One particular amino acid transported by B0AT1, tryptophan, is needed to produce vitamin B3 (also known as niacin).

SLC6A19 gene mutations result in the production of a B0AT1 protein with reduced activity. As a result, specific amino acids cannot be taken in by cells and are instead removed from the body as waste. Because these amino acids are removed from the body without being used, people with this condition may be lacking (deficient) in certain amino acids and vitamins. However, individuals who are nutrient-deficient due to their diet, illness, stress, or a variety of other reasons, can develop serious signs and symptoms of this condition including rashes, cerebellar ataxia , and psychiatric symptoms. Researchers believe that many of these features are related to a deficiency of tryptophan and niacin, specifically.

Source: GHR (NLM/NIH)1

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Inheritance Pattern

This condition is inherited in an autosomal recessive pattern , which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Source: GHR (NLM/NIH)2

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Learn more about the gene associated with Hartnup disease

  • SLC6A19

Source: GHR (NLM/NIH)3

Inheritance of Hartnup disease

Genetic and familial features of the condition may include:4 Genetics of Hartnup disease:

  • Autosomal recessive inheritance

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  1. Source: GHR (NLM/NIH): condition/ hartnup-disease
  2. ibid.
  3. ibid.
  4. Source: Human Phenotype Ontology

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