A young girl with scleroderma and 21 members of her family were studied for their ability to metabolize tryptophan by the pathway which leads to nicotinic acid. Nine of ten female members of the family and two of 12 males had abnormal tryptophan metabolism.
The metabolic disorder was characterized by a pattern of urinary tryptophan metabolities in which kynurenine was the major excretory product of the tryptophan-nicotinic acid pathway, with one or more of the following metabolites present in greater than normal quantities: o-aminohippuric acid, kynurenic acid, or acetylkynurenine. This metabolic disorder differs from hydroxykynureninuria by the pattern of urinary tryptophan metabolites, and from the hereditary disorder of tryptophan metabolism described by Knapp by the pattern of urinary tryptophan metabolites and the response of that condition to the administration of pyridoxine.
Price JM, Yess N, Brown RR, Johnson SAM. Tryptophan MetabolismA Hitherto Unreported Abnormality Occurring in a Family. Arch Dermatol. 1967;95(5):462-472. doi:10.1001/archderm.1967.01600350024004