Pellagra

Definition:
Pellagra is a nutritional disorder caused by niacin (vitamin B₃) deficiency or its precursor tryptophan deficiency.

Cause:

• Dietary deficiency (maize-based diet low in niacin & tryptophan)

• Hartnup disease, carcinoid syndrome, chronic alcoholism

• Drugs: isoniazid, hydantoin

Key Features: "3 Ds"

• Dermatitis – photosensitive, hyperpigmented rash on exposed areas

• Diarrhea – due to GI mucosal atrophy

• Dementia – neurological symptoms from NAD/NADP deficiency
  (If untreated → 4th D: Death)

Biochemical Basis:
Niacin is essential for NAD⁺ & NADP⁺ synthesis → Required in energy metabolism (oxidation–reduction reactions).

Real Data:

• RDA for niacin: ~14–16 mg/day (adults)

• 60 mg dietary tryptophan ≈ 1 mg niacin