<prompt> Bone within bone appearance is classically seen inOsteomalaciaOsteopetrosisRenal osteodystrophyVitamin C deficiency  <response>: Ans. b OsteopetrosisRef: Sutton 7th1339,1355, 1365DiseaseRadiological featureOsteoporosis Cod fish vertebrae Pencilling-in-vertebrae loss of density of vertebral body with radiodense end platesOsteomalacia Loosers zone Pseudo fracture is the Hallmark feature BL radiolucent band of uncalcified osteoid due to pressure of pulsating artery Cod Fish marked biconcave vertebrae Pencilling in vertebraeOsteopetrosis Marble Bone diseaseAlberg Schowenberg disease Bone within Bone appearance Erlenmeyer flask deformity of long bone disease ends flask shaped metaphysis Rugger jersey spine Increased density of bones 