Hartnup disease

Hartnup disease (also known as "pellagra-like dermatosis" and "Hartnup disorder") is an autosomal recessive metabolic disorder affecting the absorption of nonpolar amino acids (particularly tryptophan that can be, in turn, converted into serotonin, melatonin, and niacin). Niacin is a precursor to nicotinamide (both are forms of vitamin B3), a necessary component of NAD+.^: 541

The causative gene, SLC6A19, is located on chromosome 5. It is named after the British family, Hartnup, who had this disease.