(hī-drok'sē-kī-nū'rĕ-ni-nū'rē-ă), [MIM*236800] An abnormality in tryptophan metabolism, probably due to a defect in kynureninase, characterized by mild mental retardation, migrainelike headaches, and urinary excretion of large amounts of kynurenine, 3-hydroxykynurenine, and xanthurenic acid; autosomal recessive inheritance.