[Pellagra: an ancient disease in a modern world].

Introduction: pellagra is a systemic disease due to deficiency of vitamin B3 or tryptophan, its precursor. Vitamin B3 is needed for several metabolic processes, cell signaling, and DNA repair. It is characterized by a classic tetrad of dermatitis, diarrhea, dementia, and death. Pellagra is considered rare nowadays; however, due to the popularity of restrictive diets without necessary supplementation such us veganism, there has been an increase in cases in recent years. Clinical case: we report the case of a young strict vegan female patient in which a pellagra diagnosis was made, and early treatment was administered with an excellent outcome. Discussion: the interest of this case lies in the importance of clinical suspicion and directed history taking focused on social and nutritional factors, as adapted for the current times, in order to make the diagnosis of a rare, subdiagnosed disease that is life-threatening if treatment is delayed.