Hartnup syndrome E72.02

Hartnup disease is an autosomal recessive metabolic disorder caused by impaired absorption of neutral amino acids in the intestines and kidneys. The clinical spectrum is broad and includes neutral amino aciduria, indicanuria, light-sensitive pellagra-like rashes, cerebellar ataxia, anxiety, depression, and mild intellectual disability.

Clinical symptoms occur intermittently and are influenced by environmental factors, seasons, stress, and malnutrition. Some patients remain asymptomatic and are diagnosed during routine examinations (Hashmi MS et al. 2026).

One of the most common hereditary disorders of amino acid transport. Prevalence: about 1/40.000 births.

Autosomal recessively inherited mutations in the "Hartnup disorder" gene (SLC6A19 gene; gene locus: 5p15). The SLC6A19 gene encodes the sodium-dependent transporter B(0)AT1 for neutral amino acids, a transmembrane transporter that actively transports most neutral amino acids across the apical membrane of epithelial cells. It is involved in amino acid import across the plasma membrane as well as in other forms of neutral amino acid transport and thus plays a central role in nutrient uptake in epithelial tissues. Its expression is high in the proximal digestive tract and the gastrointestinal tract, and high protein expression has also been detected in the hepatobiliary system. 

Areas of skin exposed to light.

Skin manifestations: Seasonal pellagra-like skin lesions with photosensitivity, redness, swelling, and itching; poikiloderma.

Extracutaneous manifestations: cerebellar ataxia, psychiatric changes.

Pellagra

Pellagroid

Phototoxic dermatitis

Photoallergic eczema

Congenital poikiloderma

Progeria-like syndrome.

Nicotinamide (e.g. Nicotinamide 200 Jenapharm) in high doses (50-300 mg/day). Protein-rich diet. Avoid greater exposure to the sun, sun protection. Monoamine oxidase inhibitors are contraindicated.

The name Hartnup comes from the family where the disease was first diagnosed.

1. Baron DN, Dent CE, Harris H, Hart EW, Jepson JB (1956) Hereditary pellagra-like skin rash with temporary cerebellar ataxia, constant renal aminoaciduria, and other unusual biochemical features. Lancet II: 421–433

2. Hashmi MS et al. (2026) Gupta V. Hartnup Disease. Feb. 13, 2023. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; Jan 2026–. PMID: 32644502.

3. Potter SJ et al. (2002) Hartnup disorder: polymorphisms identified in the neutral amino acid transporter SLC1A5. J Inherit Metab Dis 25: 437–448

4. Zheng Y et al. (2009) A novel missense mutation in the SLC6A19 gene in a Chinese family with Hartnup disorder. Int J Dermatol. Apr 2009;48(4):388-92.