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Hartnup disorder
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.
Metabolic
Metabolism refers to all the physical and chemical processes in the body that convert or use energy, such as:BreathingCirculating bloodControlling bo...
Amino acids
Amino acids are organic compounds that combine to form proteins. Amino acids and proteins are the building blocks of life. When proteins are digeste...
Tryptophan
Tryptophan is an amino acid needed for normal growth in infants and for nitrogen balance in adults. It is an essential amino acid. This means your ...
Causes
Hartnup disorder is possibly the most common metabolic condition involving amino acids. It is an inherited condition. 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 5 years.
Symptoms
Most people show no symptoms. If symptoms do occur, they most often appear in childhood and may include:
- Diarrhea
- Mood changes
- Nervous system (neurologic) problems, such as abnormal muscle tone
-
Red, scaly
skin rash
, usually when skin is exposed to sunlight
Skin rash
Rashes involve changes in the color, feeling or texture of your skin.
Read Article Now Book Mark Article - Sensitivity to light (photosensitivity)
-
Short stature
Short stature
A child who has short stature is much shorter than children who are the same age and sex. Your health care provider will go over your child's growth ...
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Uncoordinated movements
Uncoordinated movements
Uncoordinated movement is due to a muscle control problem that causes an inability to coordinate movements. It leads to a jerky, unsteady, to-and-fr...
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Exams and Tests
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.
Health care providers can test for the gene that causes Hartnup disease, SLC6A19. Biochemical tests are also available.
Treatment
Treatments include:
- Avoiding sun exposure by wearing protective clothing and using a sunscreen with a protection factor of 15 or higher
- Eating a high-protein diet
- Taking supplements containing nicotinamide
- Undergoing mental health treatment, such as taking antidepressants or mood stabilizers, if mood swings or other mental health problems occur
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:
- Changes in skin color that are permanent
- Mental health problems
- Rash
- Uncoordinated movements
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.
Prevention
Genetic counseling may help prevent some cases. Eating a high-protein diet may prevent amino acid deficiencies that cause symptoms.
References
Gibson KM, Pearl PL. Inborn errors of metabolism and the nervous system. In: Daroff RB, Jankovic J, Mazziotta JC, Pomeroy SL, eds. Bradley's Neurology in Clinical Practice . 7th ed. Philadelphia, PA: Elsevier; 2016:chap 91.
Kliegman RM, Stanton BF, St. Geme JW, Schor NF. Defects in metabolism of amino acids. In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics . 20th ed. Philadelphia, PA: Elsevier; 2016:chap 85.
Review Date: 8/16/2016
Reviewed By: Anna C. Edens Hurst, MD, MS, Assistant Professor in Medical Genetics at the University of Alabama, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
