Hartnup disease: Overview

Hartnup disease is a condition caused by the body's inability to absorb certain protein building blocks (amino acids) from the diet. As a result, affected individuals are not able to use these amino acids to produce other substances, such as vitamins and proteins. Most people with Hartnup disease are able to get the vitamins and other substances they need with a well-balanced diet.

People with Hartnup disease have high levels of various amino acids in their urine (aminoaciduria). For most affected individuals, this is the only sign of the condition. However, some people with Hartnup disease have episodes during which they exhibit other signs, which can include skin rashes; difficulty coordinating movements (cerebellar ataxia); and psychiatric symptoms, such as depression or psychosis. These episodes are typically temporary and are often triggered by illness, stress, nutrient-poor diet, or fever. These features tend to go away once the trigger is remedied, although the aminoaciduria remains. In affected individuals, signs and symptoms most commonly occur in childhood.

Source: GHR (NLM/NIH)1

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Summary

Hartnup disease is a metabolic disorder characterized by abnormal transport of certain amino acids in the kidney and gastrointestinal system. It is a type of aminoaciduria. The condition may be diagnosed based on the results of newborn screening tests. Most people with the condition have no symptoms (asymptomatic). For those who do show symptoms, the onset of the disease is usually between the ages of 3 and 9; occasionally the disease may present in adulthood. Mental development is usually normal, though a few cases with intellectual impairment have been reported. The signs and symptoms of Hartnup disease incude skin photosensitivity, neurologic findings, psychiatric symptoms, and ocular (eye) findings. Hartnup disease is caused by mutations in the SLC6A19 gene and is inherited in an autosomal recessive manner.[1, 2] People with Hartnup disease may benefit from a high-protein diet, protection from sunlight, vitamin supplementation, and avoidance of certain drugs/medications. In some cases, treatment with nicotinamide supplements and tryptophan ethyl ester may be indicated. [1, 2]

Last updated: 12/17/2015

Source: GARD (NIH)2

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Hartnup Disease: An autosomal recessive inherited metabolic disorder caused by mutations in the SLC6A19 gene. It is characterized by defective absorption of neutral amino acids. Signs and symptoms include skin eruptions reminiscent of pellagra, aminoaciduria, and cerebellar ataxia.3

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Hartnup Disease: An autosomal recessive disorder due to defective absorption of Neutral Amino Acids by both the intestine and the Proximal Renal Tubules. The abnormal urinary loss of Tryptophan, a precursor of Niacin, leads to a Nicotinamide deficiency, Pellagra-like light-sensitive rash, Cerebellar Ataxia, emotional instability, and aminoaciduria. Mutations involve the neurotransmitter transporter gene Slc6A19.4

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Hartnup disease: An amino acid metabolic disorder that is caused by abnormalities of the renal tubules and is characterized especially by aminoaciduria involving only monocarboxylic monoamines, a dry red scaly rash, and episodic muscular incoordination due to the effects of the disease on the cerebellum.5

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Hartnup disease is a rare metabolic disorder belonging to the neutral aminoacidurias and characterized by abnormal renal and gastrointestinal transport of neutral amino acids (tryptophan, alanine, asparagine, glutamine, histidine, isoleucine, leucine, phenylalanine, serine, threonine, tyrosine and valine).6

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References

  1. Source: GHR (NLM/NIH): ghr.nlm.nih.gov/ condition/ hartnup-disease
  2. Source: GARD (NIH): rarediseases.info.nih.gov/ diseases/ 6569/ hartnup-disease
  3. Source: NCI Thesaurus
  4. Source: MeSH (U.S. National Library of Medicine)
  5. Source: Disease Ontology
  6. Source: Monarch Initiative

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