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: Social & Preventive Medicine
[{'content': 'Excess of leucine causes: \nSelect and explain. \nA. Pellagra, B. Constipation, C. Hypervitarninosis, D. Progeria', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Pellagra', 'role': 'assistant'}]