Pellagra is caused due to deficiency of niacin (nicotinic acid or nicotinamide). Thiamine (vitamin- $ {{B}_{1}} $ ) deficiency causes beri- beri in humans and polyneuritis in animals, pyridoxine (vitamin-Be) deficiency causes anaemia, neuritic pain, convulsions, skin lesions, while biotic (vitamin- $ {{B}_{6}} $ ) deficiency causes dermatitis.