A 10 year old girl presented with clinical signs and symptoms of the triad of niacin deficiency namely skin eruptions, ataxia, mental changes and diarrhea. Although this deficiency could be nutritional where maize is a staple diet, this patient had neutral aminoaciduria which indicated a defective transport of neutral amino acid transporter in the kidneys and intestine resulting in failure of transport of tryptophan and other neutral (ie, monoaminomonocarboxylic) alpha-amino acids in the small intestine and the renal tubules.