Home > D. Systemic pathology > Genetic and developmental anomalies > Genetic metabolic diseases > Hartnup disease
Hartnup disease
MIM.234500 eM.derm/713
Friday 1 August 2008
Definition: Hartnup disease is an autosomal recessive genetic metabolic disorder in the absorption of neutral amino acids, particularly tryptophan.
Tryptophan can be converted into serotonin, melatonin and niacin. Niacin is a precursor to nicotinamide, a necessary component of NAD+.
The causative gene, SLC6A19, is located on chromosome 5.
Synopsis
failure to thrive photosensitivity intermittent ataxia nystagmus tremor
Nicotinamide
Nicotinamide is necessary for neutral amino acid transporter production in the proximal renal tubules found in the kidney, and intestinal mucosal cells found in the small intestine. Therefore, a symptom stemming from this disorder results in increased amounts of amino acids in the urine.
See also
pellagra (also caused by low nicotinamide)