Pellagra with colitis due to a defect in tryptophan metabolism.

A 9-year-old girl presented with a red scaly rash confined to sun-exposed areas which started at 2 years of age and had the appearance of pellagra. Investigation of urinary tryptophan metabolites following an oral tryptophan load, showed increased excretion of kynurenine and kynurenic acid but reduced excretion of 3-hydroxy-kynurenine, xanthurenic acid and N1-methyl nicotinamide. These results indicated a defect in the hydroxylation of kynurenine, an important reaction in the synthesis of the nicotinamide nucleotide coenzymes, NAD and NADP, from tryptophan. The patient went on to develop severe colitis and psychological changes. All her symptoms responded to treatment with nicotinamide.