This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitamins and Minerals, Subject name: Biochemistry
[{'content': "Pellagra is caused by - \nSelect and explain. \nA. Hartnup's disease, B. Cystinuria, C. Cystinosis, D. Type I Tyrosinemia", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Hartnup's diseaseHartnup's disease* It is a defect of neutral aminoacid transporter which is specific for tryptophan. This transporter is responsible for tryptophan absorption along intestine as well as tryptophan reabsorption across renal tubules.* When tryptophan is not absorbed, tryptophan can not be converted into niacin (Niacin is endogenously synthesised from tryptophan). Hence it presents as pellagra.* As the transporter is also related to tryptophan reabsorption along renal tubules, tryptophan will be lost in the urine. Hence it presents as aminoaciduria.", 'role': 'assistant'}]