The Forgotten Vitamin: A Modern Case of Niacin Deficiency Presenting with the Classic Three Ds’ Manifestations

Background Pellagra, a disease caused by niacin (vitamin B3) deficiency, is characterized by the "3 Ds": dermatitis, diarrhea, and dementia. While rare in industrialized nations, it persists in at-risk populations, particularly those with alcohol use disorder, malabsorption, or post-bariatric surgery. Case presentation This case presents a 64-year-old woman with chronic alcohol dependence and a history of sleeve gastrectomy, who developed advanced pellagra. Her clinical symptoms included a diffuse pruritic rash, diarrhea, cognitive decline, and severe leg pain. Clinical exams was notable for a symmetric hyperpigmented rash on both forearms, the neck and the upper back. Laboratory tests confirmed a significantly low serum niacin level (< 20). Initial diagnoses, such as toxic shock syndrome or Stevens-Johnson syndrome, were ruled out after a skin biopsy showed nonspecific spongiotic dermatitis. After starting oral niacin supplementation, gastrointestinal and dermatologic symptoms improved, though her cognitive impairment persisted. The patient’s condition was complicated by sepsis, acute kidney injury, and multi-organ failure, leading to eventual brain death. Discussion This case highlights the challenges of diagnosing pellagra in a modern clinical setting, especially when compounded by other medical conditions. Despite early treatment, delayed recognition and aggressive systemic complications contributed to a fatal outcome. It underscores the importance of considering secondary pellagra in patients with risk factors and the need for early diagnosis and niacin replacement to prevent severe outcomes.