Hartnup disorder


Hartnup disorder is a genetic condition in which there is a defect in the transport of certain amino acids (such as tryptophan and histidine) by the small intestine and kidneys.


Hartnup disorder is a metabolic condition involving amino acids. It is an inherited condition. This condition occurs due to mutation in the SLC6A19 gene. A child must inherit a copy of the defective gene from both parents in order to be seriously affected.

The condition most often appears between ages 3 to 9 years.


Most people show no symptoms. If symptoms do occur, they most often appear in childhood and may include:

Exams and Tests

The health care provider will order a urine test to check for high levels of neutral amino acids. The levels of other amino acids may be normal.

Your provider can test for the gene that causes this condition. Biochemical tests may also be ordered.


Treatments include:

Outlook (Prognosis)

Most people with this disorder can expect to live a normal life with no disability. Rarely, there have been reports of severe nervous system disease and even deaths in families with this disorder.

Possible Complications

In most cases, there are no complications. Complications when they occur may include:

Nervous system symptoms can most often be reversed. However, in rare cases they can be severe or life threatening.

When to Contact a Medical Professional

Call for your provider if you have symptoms of this condition, especially if you have a family history of Hartnup disorder. Genetic counseling is recommended if you have a family history of this condition and are planning a pregnancy.


Genetic counseling prior to marriage and conception may help prevent some cases. Eating a high-protein diet may prevent amino acid deficiencies that cause symptoms.

Review Date: 7/26/2018
Reviewed By: Anna C. Edens Hurst, MD, MS, Assistant Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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