Pellagra in the USA: unusual manifestations of a rare entity

The case involves a 62-year-old female native of the USA with a history of bipolar disorder and chronic obstructive pulmonary disease who presented with intractable diarrhoea. Prior to the index admission, she was admitted to the intensive care unit and required pericardiocentesis for an idiopathic pericardial effusion with tamponade physiology. Following discharge, she suffered intractable diarrhoea and represented for medical evaluation. She had a painful, swollen tongue as well as persistent hypoglycaemia and required glucose infusions. She had adrenal function testing which revealed adrenal insufficiency. Vitamin testing revealed normal B₁₂ and folate levels but undetectable levels of thiamine, riboflavin and niacin. Her symptoms and signs resolved entirely with appropriate vitamin supplementation. Niacin (vitamin B₃) is essential for multiple metabolic pathways, and severe deficiency may cause clinical syndrome of pellagra which is most commonly associated with diarrhoea, delirium and dermatitis. Additional physiological derangements may include adrenal insufficiency, insulin hypersensitivity and pericarditis.