avitaminosis caused by a vitamin PP (nicotinic acid) deficiency. It is manifested by disorders of the skin (dermatitis, generally on the face and neck), alimentary canal (ulceration of the lingual and intestinal mucosa and impairment of gastric secretion and motility), and nervous system (polyneuritis). Treatment involves the administration of nicotinic acid, usually combined with other B-complex vitamins, and adherence to a balanced diet, which includes foods rich in the B vitamins (yeast, liver, eggs, beans) and tryptophan (milk), from which vitamin PP is synthesized in the body.