Casal necklace is seen in?

Casal necklace is seen in: Pellagra Due to deficiency of Niacin / Vitamin B3. Tryptophan is used to produce niacin. Niacin deficiency occurs in hanup disease (defect in the transpoation of neutral amino acids) , maize-based diets and carcinoid syndrome. Characterised by 3Ds- Diarrhea, Dermatitis (Casal necklace), Dementia, and finally death.