Pellagra is a vitamin deficiency disease that is often reported in Africa, Central America, and South-east Asia. Caused by tryptophan and niacin-poor diets, it has also been identified in marginalized individuals in industrial societies (especially homeless, chronic alcoholic, and psychiatric patients who refuse food). Symptoms of pellagra include light sensitivity, dementia, diarrhea, and dermatitis. In advanced cases, pellagra can lead to psychotic delusions. Left untreated, pellagra cases die after several years without proper nutrition.
While first identified in Spain in the 18th century, it received its name from an epidemic in Italy ("pelle agra" means bitter skin in Italian). Pellagra was epidemic in parts of the US in the early 1900s before the nutritional basis for the disease was identified and niacin supplements made treatment possible. While easy to diagnose and treat, physicians often miss vital clues, especially in industrialized societies where pellagra is less likely to be encountered. Even in non-industrialized countries, improved standard of living and a greater diversity in dietary source have made pellagra less common.
A recent article in the American Journal of Therapeutics discusses the possible resurgence of pellagra in HIV patients and anorexia nervosa patients who neglect proper nutrition. The authors discuss a case of pellagra identified through the warning triad of "dermatosis, diarrhea, and dementia" and properly treated.