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: Pediatrics
[{'content': 'Hair on end appearance is seen in X–ray skull in –a)  Thalassemiab)  Hydrocephalusc)  Chronic malariad)  Sickle cell anemia \nSelect and explain. \nA. ad, B. c, C. ac, D. ab', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Bone Changes in Thalassemia \n\nBones become thin and pathological fracture may occur.\nMassive expansion of the marrow of fade and skull produces characteristics .facies.\nSevere maxillary hyperplasia and malocclusion.\nProminant widening of diploic spaces with "hair on end appearance" caused by vertical trabeculae.\nCrew-cut appearance → striking expansion of hematopoietically active marrow that erodes existing cortical bone and induces new bone formation giving rise to crew cut appearance.\n\nCauses of "Hair on end appearance" →Sickle cell anemia, hereditary spherocytosis, G-6-PD deficiency', 'role': 'assistant'}]