Pellagra

Pellagra
The skin features of pellagra including peeling, redness, scaling, and thickening of sun-exposed areas.
Specialty	Dermatology
Symptoms	Inflammation of the skin, diarrhea, dementia, sores in the mouth[1]
Types	Primary, secondary[1]
Causes	Not enough niacin[2]
Diagnostic method	Based on symptoms[3]
Differential diagnosis	Kwashiorkor, pemphigus, photodermatitis, porphyria[3]
Prevention	Consuming Niacin
Treatment	Nicotinic acid or nicotinamide supplementation.[1]
Prognosis	Good (with treatment), death in ~ 5 years (without treatment)[3]
Frequency	Rare (developed world), relatively common (developing world)[3]

Pellagra is a disease caused by a lack of the vitamin niacin (vitamin B₃).^[2] Symptoms include inflamed skin, diarrhea, dementia, and sores in the mouth.^[1] Areas of the skin exposed to friction and radiation are typically affected first.^[1] Over time affected skin may become darker, stiffen, peel, or bleed.^[1][3]

There are two main types of pellagra, primary and secondary.^[1] Primary pellagra is due to a diet that does not contain enough niacin and tryptophan.^[1] Secondary pellagra is due to a poor ability to use the niacin within the diet.^[1] This can occur as a result of alcoholism, long-term diarrhea, carcinoid syndrome, Hartnup disease, and a number of medications such as isoniazid.^[1] Diagnosis is typically based on symptoms and may be assisted by urine testing.^[3]

Treatment is with either nicotinic acid or nicotinamide supplementation.^[1] Improvements typically begin within a couple of days.^[1] General improvements in diet are also frequently recommended.^[3] Decreasing sun exposure via sunscreen and proper clothing is important while the skin heals.^[1] Without treatment death may occur.^[3] The disease occurs most commonly in the developing world, often as a disease of poverty associated with malnutrition, specifically sub-Saharan Africa.^[3]