Hartnup disease

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Hartnup disease (hart-nup) n. a rare hereditary defect in the absorption of the amino acid tryptophan, leading to mental retardation, thickening and roughening of the skin on exposure to light, and lack of muscular coordination. The condition is similar to pellagra. Treatment with nicotinamide is usually effective. [Hartnup family, in whom it was first reported]

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