A patient presented with diarrhea, dermatitis, and dementia. Which of the following vitamin deficiencies would you suspect in this patient?

Correct Answer: D. Vitamin B3 deficiency

The classic triad of diarrhea, dermatitis, and dementia (the "4 Ds" when including death) is pathognomonic for niacin (Vitamin B3) deficiency, also known as pellagra. Niacin is an essential cofactor for NAD+ and NADP+-dependent enzymes involved in energy metabolism, DNA repair, and cellular signaling. Deficiency leads to multi-system involvement: gastrointestinal mucosa becomes inflamed (diarrhea), skin exposed to sunlight develops symmetric photosensitive dermatitis (especially on face, neck, hands, and feet), and CNS involvement manifests as depression, anxiety, and cognitive decline progressing to dementia. In India, pellagra historically occurred in populations consuming corn-based diets without niacin supplementation (particularly in certain regions of Maharashtra and Madhya Pradesh). The disease is preventable and reversible with niacin supplementation (50–100 mg daily). The pathophysiology involves impaired NAD+-dependent cellular respiration, leading to cell death in high-metabolic tissues (GI epithelium, skin, brain). Modern India sees pellagra rarely due to fortification of wheat flour, but it remains a consideration in malnourished populations, alcoholics, and those with malabsorption syndromes.

Why the other options are wrong

A. Vitamin B12 deficiency — B12 deficiency causes megaloblastic anemia, glossitis, and peripheral neuropathy (paresthesias, ataxia), not the photosensitive dermatitis or acute diarrhea seen in pellagra. Neurological manifestations are subacute/chronic and involve posterior columns, not acute dementia. The triad of diarrhea–dermatitis–dementia is not characteristic of B12 deficiency. B. Vitamin B1 deficiency — Thiamine deficiency causes beriberi (wet or dry) and Wernicke–Korsakoff syndrome, characterized by ophthalmoplegia, ataxia, and confabulation—not the photosensitive dermatitis or diarrhea of pellagra. B1 deficiency is associated with alcoholism in India but does not produce the classic 4 Ds triad. C. Vitamin B6 deficiency — Pyridoxine deficiency causes peripheral neuropathy, seizures, and seborrheic dermatitis around eyes and mouth, but NOT the symmetric photosensitive dermatitis on sun-exposed areas characteristic of pellagra. Diarrhea and dementia are not hallmark features of B6 deficiency.

High-Yield Facts

Mnemonics

4 Ds of Pellagra Diarrhea, Dermatitis (photosensitive), Dementia, Death—the classic tetrad of niacin (B3) deficiency. Use when you see this triad in an exam question. NIACIN = NAD+ Deficiency Niacin is the precursor for NAD+/NADP+. Without it, cellular respiration fails in high-energy tissues (gut, skin, brain). Remember: no NAD+ → no energy → cell death in metabolically active organs.

NBE Trap

NBE may pair pellagra with alcoholism (true risk factor) but offer B1 deficiency (Wernicke–Korsakoff) as a distractor, since both are alcohol-related. The discriminator is the photosensitive dermatitis and diarrhea—unique to niacin deficiency.

Clinical Pearl

In rural India, a malnourished patient with symmetric erythema on the face and neck (sparing covered areas) + diarrhea + behavioral changes should trigger immediate niacin supplementation. Early recognition prevents irreversible neurological damage and death. Isoniazid-treated TB patients are at particular risk and should receive niacin prophylaxis.

_Reference: KD Tripathi Pharmacology Ch. 47 (Vitamins); Robbins Pathology Ch. 8 (Nutritional Disorders); Harrison Principles of Internal Medicine Ch. 96 (Vitamin Deficiencies)_