Pellagra is a vitamin deficiency disease most commonly caused by a chronic lack of niacin (vitamin B3) in the diet. It can be caused by decreased intake of niacin or tryptophan, and possibly by excessive intake of leucine. It may also result from alterations in protein metabolism in disorders such as carinoid syndrom. A deficiency of the amino acid lysine can lead to a deficiency of niacin as well, meaning that another potential cause of pellagra is lysine deficiency.