Pellagra  is a disease caused by a lack of the vitamin niacin (vitamin B3). Symptoms include inflamed skin, diarrhea, dementia, and sores in the mouth. Areas of the skin exposed to either sunlight or friction are typically affected first. Over time affected skin may become darker, stiffen, peel, or bleed.There are two main types of pellagra, primary and secondary. Primary pellagra is due to a diet that does not contain enough niacin and tryptophan. Secondary pellagra is due to a poor ability to use the niacin within the diet. This can occur as a result of alcoholism, long-term diarrhea, carcinoid syndrome, Hartnup disease, and a number of medications such as isoniazid. Diagnosis is typically based on symptoms and may be assisted by urine testing.Treatment is with either niacin or nicotinamide supplementation. Improvements typically begin within a couple of days. General improvements in diet are also frequently recommended. Decreasing sun exposure via sunscreen and proper clothing is important while the skin heals. Without treatment death may occur. The disease occurs most commonly in the developing world, often as a disease of poverty associated with malnutrition, specifically sub-Saharan Africa. Signs and symptoms
The classic symptoms of pellagra are diarrhea, dermatitis, dementia, and death ("the four Ds"). A more comprehensive list of symptoms includes:

Sensitivity to sunlight
Dermatitis (characteristic "broad collar" rash known as casal collar)
Hair loss
Swelling
Smooth, beefy red glossitis (tongue inflammation)
Trouble sleeping
Weakness
Mental confusion or aggression
Ataxia (lack of coordination), paralysis of extremities, peripheral neuritis (nerve damage)
Diarrhea
Dilated cardiomyopathy (enlarged, weakened heart)
Eventually dementiaJ.
If maize is not nixtamalized, it is a poor source of tryptophan, as well as niacin. Nixtamalization corrects the niacin deficiency, and is a common practice in Native American cultures that grow corn, but most especially in Mexico and the countries of Central America. Following the corn cycle, the symptoms usually appear during spring, increase in the summer due to greater sun exposure, and return the following spring. Indeed, pellagra was once endemic in the poorer states of the U.S. South, such as Mississippi and Alabama, where its cyclical appearance in the spring after meat-heavy winter diets led to it being known as "spring sickness" (particularly when it appeared among more vulnerable children), as well as among the residents of jails and orphanages as studied by Dr. Joseph Goldberger.Pellagra is common in Africa, Indonesia, and China. In affluent societies, a majority of patients with clinical pellagra are poor, homeless, alcohol-dependent, or psychiatric patients who refuse food. Pellagra was common among prisoners of Soviet labor camps (the Gulags). In addition, pellagra, as a micronutrient deficiency disease, frequently affects populations of refugees and other displaced people due to their unique, long-term residential circumstances and dependence on food aid. Refugees typically rely on limited sources of niacin provided to them, often peanuts (which, in Africa, may be supplied in place of local groundnut staples, such as the Bambara or Hausa groundnut); the instability in the nutritional content and distribution of food aid can be the cause of pellagra in displaced populations.