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
[{'content': "A 15 year old female patient presents with pain in the calf muscles on exercise. Routine investigation reveals\xa0burgundy-colored urine (sample obtained after exercise).\xa0Histopathology of muscle shows deposits of glycogen in an excess amount. What is the diagnosis? \nSelect and explain. \nA. Von Gierke's disease, B. Pompe's disease, C. McArdle's disease, D. Cori's disease", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Type V Glycogen Storage Disease\xa0(McArdle Disease)\n\nType V GSD is an autosomal recessive disorder.\n\nBiochemical Defect:\n\nMuscle Phosphorylase Defect.\nThe gene for muscle phosphorylase (PYGM) has been mapped to chromosome 11q13.\nLack of this enzyme limits muscle ATP generation by\xa0 glycogenolysis,\xa0resulting\xa0in\xa0muscle\xa0glycogen accumulation, and is the prototype of muscle energy disorders.\n\nClinical Manifestations:\n\nSymptoms usually 1st develop in late childhood or as an adult and are characterized by exercise intolerance with muscle cramps and pain.\xa0\nMany patients experience a characteristic ‘second wind’ phenomenon.\xa0If\xa0 they\xa0slow\xa0down or pause briefly at the 1st appearance of muscle pain, they can resume exercise with more ease.\nAbout\xa050%\xa0of\xa0patients\xa0report\xa0burgundy-colored urine after exercise,\xa0which\xa0is\xa0the\xa0consequence of exercise-induced\xa0myoglobinuria,\xa0secondary\xa0to rhabdomyolysis.\n\nKey Concept:\nBurgundy-colored urine after exercise\xa0is\xa0the\xa0consequence of exercise-induced\xa0myoglobinuria,\xa0secondary\xa0to rhabdomyolysis. It occurs in\xa0Type V Glycogen Storage Disease\xa0(McArdle Disease).\nReference- Harper’s illustrated biochemistry. 30th edition page no: 179', 'role': 'assistant'}]