<prompt> Niacin deficiency causesPigmentationDiarrheaRashLactic acidosis  <response>: Deficiency of niacin: A deficiency of niacin causes pellagra, a disease involving the skin, gastrointestinal tract, and CNS. The symptoms of pellagra progress through the three Ds: dermatitis, diarrhoea, dementia--and, if untreated, death. Reference: Lippincott Textbook of Biochemistry pg no. 380 