Abstract
A new hereditary defect of tryptophan metabolism is described in a Sudanese family with a high degree of consanguinity. It has an autosomal recessive pattern of inheritance. The condition manifests as a pellagra-like skin rash within 8 weeks after birth, with signs of cerebellar ataxia and developmental retardation. Cataracts develop early, and to date none of the ten affected children has survived beyond 2 years of age. Biochemically, the condition is characterized by an apparent impairment of the ability to synthesize quinolinic acid and nicotinamide nucleotides from tryptophan, which might be due to abnormally high activity of the enzyme picolinate carboxylase.