This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Dementia, dermatitis, diarrhoea are features of 
Select and explain. 
A. Bed Bed, B. Pellagra, C. Vitamin B12 deficiency, D. Pyridoxine deficiency
B: Pellagra
Answer: B: Pellagra 
Explanation: Deficiency of niacin causes pellagra, a disease involving the skin, gastrointestinal tract, and CNS. 
The symptoms of pellagra progress through the three Ds: dermatitis (photosensitive), diarrhea, and dementia. If untreated, death (a fourth D) occurs. 
Hartnup disorder, characterized by defective absorption of tryptophan, can result in pellagra-like symptoms.

Ref : Lippincott’s illustrated reviews for biochemistry , 7th edition.