Pellagra, an Almost-Forgotten Differential Diagnosis of Chronic Diarrhea: More Prevalent Than We Think.

Pellagra, caused by vitamin B3 (niacin) deficiency, is traditionally described as dermatitis, diarrhea, dementia (3D), and even death (4D) syndrome if not recognized and treated promptly. Although full-blown pellagra with all 3D features has become rare, pellagra still exists, especially in high-risk populations, which is actually more prevalent than we think. We report that a recently treated patient with the full spectrum of 3D clinical features of pellagra presents as chronic diarrhea of unknown etiology for 1 year. It reminds us that keeping a high index of suspicion and maintaining a broad differential diagnosis are critical for recognition and management of this potentially fatal but treatable condition.