Pellagra is caused by deficiency of niacin or its amino acid precursor tryptophan. Clinical features are characterized by dermatitis, dementia and diarrhea. Dermatitis is observed only in 33% of patients. We report a 110-year-old woman, with history of diarrhea and dementia, who presented a bilateral and symmetrical dermatosis, characterized by welldemarcated violaceous plaques due to sun exposition. Dermatological symptoms had directed investigations. Pellagra was diagnosed and treatment with supplement and oral niacin was started, with significant improvement.