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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
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.