PELLAGRA

nutritional disorder caused in large part by a deficiency of niacin, a member of the vitamin B complex, and characterized by skin lesions and by gastrointestinal and neurological disturbancesthe so-called classical three Ds of pellagra: dermatitis, diarrhea, and dementia. The skin lesions are the most characteristic and usually the earliest symptoms. They result from an abnormal sensitization of the skin to sunlight and tend to occur symmetrically on the exposed surfaces of the arms, legs, and neck. They may look at first like a severe sunburn, later becoming reddish brown, rough, and scaly. Gastrointestinal symptoms usually consist of alternate constipation and diarrhea, with an accompanying inflammation of the mouth and the tongue, and fissuring and dry scaling of the lips and corners of the mouth. Neurological signs appear later in most cases, when the skin and alimentary manifestations are prominent. The dementia, or mental aberrations, may include general nervousness, confusion, depression, apathy, and delirium. In humans, pellagra is seldom a deficiency of niacin alone; response to niacin therapy tends to be partial, whereas the therapeutic administration of multivitamins commonly brings swift recovery. Mild or suspected instances of niacin deficiency can be effectively treated with a well-balanced diet alone. The breakthrough in the understanding of pellagra took place in 1937, when it was shown that the disorder known as black tongue in dogs could be cured by the administration of niacin (also called nicotinic acid) or the amide of niacin (nicotinic acid amide or nicotinamide). Pellagra is now seldom encountered in countries in which the population generally eats a well-balanced diet, but it still occurs in people whose diet consists predominantly of corn (maize) and contains little or no protein-rich food. Corn is low in both niacin and tryptophan, the latter being an amino acid that is converted to niacin in the body. Such foods as milk and eggs, although low in niacin, will protect the body from pellagra because their proteins contain sufficient tryptophan for the synthesis of niacin. Pellagra can also be a side effect of chronic alcoholism. Symptoms closely resembling those of pellagra are seen in Hartnup disease (q.v.).