This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oncology, Subject name: Medicine
[{'content': 'A 15-year-old boy develops symptoms of renal colic. The stone eventually passes spontaneously, but it is not recovered. The urinalysis reveals hexagonal crystals, and a cyanide- nitroprusside test on the urine is positive. Which of the following is the most likely diagnosis? \nSelect and explain. \nA. cystinuria, B. thalassemia, C. hereditary glycosuria, D. primary hyperoxaluria', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Cystinuria is a congenital disorder associated with decreased tubular resorption of cystine, arginine, ornithine, and lysine. Only cystine is insoluble and is the cause of renal calculi. The typical hexagonal crystals are most likely to be seen on an acidic early-morning urine specimen. A positive cyanide-nitroprusside screening test should be confirmed by chromatography.', 'role': 'assistant'}]