Background Deficiency in the water-soluble vitamin B3
Also known as pellagra
Risk factors include:
Resource-limited countries were diet is heavy in untreated corn or sorghum (India, parts of China, and Africa; in Mexico, corn is treated and pellagra is rare)
Alcohol use disorder
Complication of bariatric surgery
Anorexia nervosa
Malabsorption
Can also be seen in carcinoid syndrome , prolonged use of isoniazid , and Hartnup disease Clinical Manifestations Classic triad of photosensitive pigmented dermatitis, diarrhea, and dementia
Causes symmetric hyperpigmented rash that looks like a sunburn, on sunexposed skin ("Casal necklace")
Also: red tongue, diarrhea, vomiting, insomnia, anxiety, disorientation, delusions, dementia, and encephalopathy Investigations Urinary N-methylnicotinamide or erythrocyte NAD:NADP ratio
