History: Pellagra was first described by Don Gasper Casal, a Spanish court physician in 1735.  It is a systemic disease of niacin deficiency.  Niacin is required for adequate cellular function and metabolism as an essential component of nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate.  As the cellular functions in multiple organs and tissues are affected by niacin deficiency, the clinical expression of pellagra is diverse.  Typically, classic pellagra is defined by the 3 Ds: dermatitis, diarrhea, and dementia. Early symptoms are usually nonspecific. Patients express weakness, lassitude, and anorexia followed by the classic symptoms of dermatitis, mental state disturbances, and GI involvement.