Pellagra (Niacin Deficiency): The Classic 4 D's

Pellagra results from niacin (vitamin B3) or tryptophan deficiency. Its hallmark features:

1. Dermatitis: Symmetric, photosensitive rash—face, neck, hands; burning, itching.
2. Diarrhea: Chronic intestinal inflammation → malabsorption, dehydration.
3. Dementia: Confusion, memory loss, depression, hallucinations.
4. Death: Untreated, progressive wasting and fatal.

Treatment: niacin supplementation + balanced diet. Early reversal is usually complete.