Hartnup disease

Hartnup disease is an inherited disorder of neutral amino acid transport in the intestine and kidneys. Impaired tryptophan absorption and reabsorption can reduce niacin availability, causing pellagra-like skin and neurological symptoms.

SLC6A19: SLC6A19 is a gene encoding the B⁰AT1 transporter for neutral amino acids in intestinal and renal epithelial cells. Variants in this gene commonly impair the transporter responsible for Hartnup disease.
Neutral amino acid: A neutral amino acid has an uncharged side chain under physiological conditions. Hartnup disease selectively disrupts transport of this broad amino acid group.
Hartnup disease diagnosis: Diagnosis of Hartnup disease combines characteristic urinary amino acid findings with clinical and genetic evidence. Neutral aminoaciduria can support diagnosis, while SLC6A19 testing can confirm it.
Charles E. Dent: Charles E. Dent was a British physician and biochemist known for research on inherited metabolic disorders. Dent and colleagues helped characterize the biochemical pattern associated with Hartnup disease.
B⁰AT1: B⁰AT1 is a sodium-dependent transporter that carries neutral amino acids across epithelial cell membranes. Its reduced activity explains defective neutral amino acid uptake in the gut and kidneys.
Amino acid transporter: An amino acid transporter is a membrane protein that moves amino acids across cell membranes. The disease arises from defective transport rather than an inability to make amino acids.
Neutral aminoaciduria: Neutral aminoaciduria is excessive urinary loss of neutral amino acids. It is a characteristic laboratory finding caused by impaired renal reabsorption.
Harriet Hartnup: Harriet Hartnup was one of the siblings in the family whose disorder was described in the first report of Hartnup disease. The disease takes its name from the family described in the original clinical account.
Tryptophan: Tryptophan is an essential amino acid used to synthesize proteins and the neurotransmitter serotonin. Poor tryptophan uptake can limit the body's production of niacin.
Intestinal absorption: Intestinal absorption is the movement of nutrients from the gut lumen into the body. Impaired absorption is one site of neutral amino acid loss in Hartnup disease.

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CystinuriaCompared with: It also causes amino-acid transport abnormalities but does not chiefly produce cystine stones.