This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Imaging of Metabolic Bone Disease, Subject name: Radiology
Bone within bone appearance is seen in - 
Select and explain. 
A. GV1L, B. Osteoporosis, C. Osteopetrosis, D. Bone infarct
C: Osteopetrosis
Answer: C: Osteopetrosis 
Explanation: Ans. is 'c' i.e., Osteopetrosis o Bone within a bone appearance may be seen in osteopetrosis.Bone within a Bone appearanceo Bone within a bone appearance is seen in : -# Normal neonate# Prostaglandin El therapy# Growth arrest/recovery lines# Heavy metal (e.g., Lead) poisoning# Bisphosphonate therapy# Hypothyroidism & Hypoparathyroidism# Sickle cell anemia# Hypercalcemia & Hypervitaminosis D# Osteopetrosis# Rickets / Osteomalacia (healed phase)# Acromegaly# Scurvy (healed phase)