Vitamin B -- nicotinic acid: Deficiency of nicotinic acid (also known as niacin), one of the B-complex vitamins, causes pellagra.

Pellagra was known as the "disease of the four D's" -- dermatitis, diarrhea, dementia and death. The disease is specifically characterized by:

• Dermatitis: A rash on areas of the skin exposed to light or trauma and ulcerations within the mouth
• Diarrhea
• Dementia: Mental disorientation, confusion, delusions and depression
• Death, if untreated.

Pellagra, once a puzzle, was solved by Joseph Goldberger (1874-1929). Serving in the Public Health Service, Dr. Goldberger proposed that pellagra was due to a nutritional deficiency and in 1915 began experiments with Mississippi prison inmates (who "volunteered" in return for full pardons). Dr. Goldberger fed them a poor diet he believed caused pellagra and within months, many developed the disease. Their symptoms of pellagra were reversed when meat, fresh vegetables and milk were added to their diet.

Niacin, Dr. Goldberger subsequently showed, was the principle that had this remarkable effect. A readily-available B vitamin, niacin cures pellagra and prevents it.

The name "pellagra" comes from the Italian "pelle", skin + "agra", rough = rough skin, referring to the skin problems in pellagra.