Pellagra is a nutritional deficiency disease caused by a lack of niacin (vitamin B3) in the diet. It is often associated with a diet high in corn and low in other nutrients. Symptoms include dermatitis, diarrhea, and dementia, which can lead to severe health issues if left untreated. The condition was first identified in the early 20th century, particularly among populations relying heavily on maize as a staple food. Treatment typically involves increasing niacin intake through diet or supplements, and with proper care, individuals can recover fully from the symptoms of pellagra.