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: Pathology
[{'content': "X-ray\xa0of a patient shows the following changes: Bulbous ends of long bones, normal appositional bone growth and there is failure of physiologic root resorption. Lab ﬁnding shows myelophthisic anemia.\xa0What can be the probable diagnosis? \nSelect and explain. \nA. Fibrous dysplasia, B. Osteomyelitis, C. Osteopetrosis, D. Paget's disease", 'role': 'user'}, {'content': 'Answer: C \nExplanation: OSTEOPETROSIS:\nRoentgenographic features:\n\nMedullary cavities are replaced by bone and the cortex is thickened.\nDensity of bone may be such that, the roots of the teeth are nearly invisible on dental roentgenogram.\nEnds of long bones are bulbous called Erlenmeyer\'s flask deformity.\nIn osteopetrosis, there is normal appositional bone growth, but failure of physiologic root resorption.\n\nOn X-ray, bones might appear club-like or show an appearance of a bone within bone (Endobone). Vertebrae are extremely radiodense and may show alternating bands, known as the "rugger-jersey" sign.\nLab findings of Osteopetrosis:\n\nMyelophthisic anemia (as bone marrow is replaced by bone).\nHypocalcemia (Shafer\xa0reports normal serum calcium, phosphorus and alkaline phosphatase levels).\nSecondary hyperparathyroidism.', 'role': 'assistant'}]