Picture 1: Typical Casal’s necklace pattern of pellagra over the ‘V’ of the neck.

Picture 2: Classical lesions of pellagra on the extensor aspect of the forearm.

Picture 3: Well defined, dry, scaly and fissured lesions of pellagra comprising the keratotic border of ‘Merck’.

Picture 4: Characteristic Casal’s collar of pellagra.

Pellagra is 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 carcinoid syndrome. A deficiency of the amino acid lysine can lead to a deficiency of niacin, as well. It is commonly observed in chronic alcoholics also.