Question:
Casal's necklace is seen in the deficiency of:
Casal's necklace is seen in the deficiency of:
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Think of the photosensitive dermatitis of the 4 D disease.
Updated On: Jun 23, 2026
- Vitamin A
- Niacin
- Iron
- Vitamin B12
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The Correct Option is B
Solution and Explanation
Step 1: Casal's necklace is a band of hyperpigmented, scaly dermatitis around the neck. It is a classic sign of pellagra, the disease of niacin (vitamin B3) deficiency.
Step 2: Pellagra results from deficiency of niacin and its precursor tryptophan. It produces the 4 Ds: dermatitis (in sun-exposed areas, including the neck collar that forms Casal's necklace), diarrhoea, dementia and, if untreated, death.
Step 3: Why the others are wrong. Vitamin A deficiency causes night blindness and xerophthalmia. Iron deficiency causes microcytic anaemia and koilonychia. Vitamin B12 deficiency causes megaloblastic anaemia and subacute combined degeneration.
Ref: DM Vasudevan, Textbook of Biochemistry, 6th edition, pg 395.
Step 2: Pellagra results from deficiency of niacin and its precursor tryptophan. It produces the 4 Ds: dermatitis (in sun-exposed areas, including the neck collar that forms Casal's necklace), diarrhoea, dementia and, if untreated, death.
Step 3: Why the others are wrong. Vitamin A deficiency causes night blindness and xerophthalmia. Iron deficiency causes microcytic anaemia and koilonychia. Vitamin B12 deficiency causes megaloblastic anaemia and subacute combined degeneration.
Ref: DM Vasudevan, Textbook of Biochemistry, 6th edition, pg 395.
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