Pellagra is due to deficiency of which vitamin?

• A. Vitamin A
• B. Vitamin B2
• C. Niacin (Vitamin B3)
• D. Vitamin C

Answer: (C)

Pellagra stems from a deficiency of niacin, also known as vitamin B3. Niacin is required to form the coenzymes NAD and NADP, which are essential for numerous redox reactions in energy metabolism and biosynthesis. When niacin is lacking, you see the classic triad of symptoms: diarrhea, a photosensitive dermatitis, and cognitive or psychiatric changes that can progress to dementia if not treated. Niacin can come directly from the diet or be produced from tryptophan, so diets very low in protein or conditions that impair tryptophan absorption or conversion (such as Hartnup disease, carcinoid syndrome, or chronic alcoholism) can lead to pellagra. The other vitamins listed—A, B2, and C—cause different deficiency syndromes (night blindness/keratomalacia, riboflavin deficiency signs like cheilosis, and scurvy, respectively), not pellagra.