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Hartnup disorder

Contents of this page:

Definition    Return to top

Hartnup disorder is an inherited metabolic condition that involves the transport of certain amino acids (for example, tryptophan and histidine) in the small intestine and kidneys.

Causes    Return to top

Hartnup disorder is possibly the most common metabolic condition involving amino acids. It is an inherited condition. A child must inherit the defective gene from both parents in order to be seriously affected.

The condition usually starts between ages 3 - 5 years.

Symptoms    Return to top

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

Exams and Tests    Return to top

A urine test that checks for high levels of "neutral" amino acids and normal levels of other amino acids may be done for this disorder.

The gene for Hartnup has been found, but DNA testing is not yet available. Biochemical tests are available.

Treatment    Return to top

Treatments include:

Outlook (Prognosis)    Return to top

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    Return to top

There are usually no complications. When they occur, complications may include:

Nervous system symptoms are usually reversible. However, in rare cases they can be severe or life-threatening.

When to Contact a Medical Professional    Return to top

Call for an appointment with your health care 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.

Prevention    Return to top

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

References    Return to top

Rezvani I. Defects in Metabolism of Amino Acids. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 85.

Update Date: 8/7/2008

Updated by: Diana Chambers, MS, EdD, Certified Genetics Counselor (ABMG), Charter Member of the ABGC, University of Tennessee, Memphis, TN. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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