Pellagra is a recurring nutritional disease associated with a severe deficiency of niacin, a vitamin of the B-complex group that includes both nicotinic acid and nicotinamide. Because the body can convert the essential amino acid tryptophan into niacin, inclusion of enough tryptophan in the diet is as effective as niacin in preventing the disease. Pellagra is usually associated with signs of deficiencies of other B complex vitamins and nearly always is linked with poverty and a diet composed substantially of maize. In recent years, pellagra in India and Egypt has been tied to consumption of another grain, jowar, a type of millet or sorghum.

Pellagra is characterized by dermatitis, diarrhea, and dementia, and thus is known as the disease of the “3 D’s.” If untreated, a fourth “D,” death, may ensue. Before the cause of the disease was known, mortality was as high as 70 percent. As knowledge about the disease increased, however, and many mild cases, previously undiagnosed, were recognized, the mortality rate was reduced substantially.

Dermatitis is the characteristic symptom of pellagra and the one on which diagnosis is based. Symmetrical lesions appear on the hands and arms, on the tops of the feet and around the ankles, on the back of the neck, and across the face in a butterflyshaped design. Weakness, a sense of malaise, and a reddened skin, sometimes confused with sunburn, are the first indications of the disease. Later the skin crusts and peels, revealing a smooth glossy skin underneath. In Spain, where the disease was first described in the eighteenth century, it was called mal de la rosa; in France, peasants named it mal de la misère.