Ans. is 'a1 i.e., Osteosarcoma o Osteosarcoma is a rare long-term complication of paget's disease.Paget diseaseo Paget's disease is characterized by increased bone turnover and enlargement and thickening of the bone, but the internal architecture is abnormal and the bone is usually brittle. Primary defect is in osteoclasts with increased osteoclastic activity. This results secondarily increase in osteoblastic activity (normal osteoclasts and osteoblasts act in a co-ordinated manner). So, characteristic cellular change is a marked increase in osteoclastic and osteoblastic activity. Bone turnover is acclerated, plasma alkaline phosphatase is raised (a sign of osteoblastic activity) and there is increased excretion of hydroxyproline in urine (due to osteoclastic activity).Clinical features of Paget's diseaseo Paget's disease is slightly more common in males and is seen after 40 years of age.o The pelvis and tibia being the commonest sites, and femur, skull, spine (vertebrae) and clavicle the next commonest.o Most of the patient with Paget's disease are asymptomatic, the disorder being diagnosed when an x-ray is taken for some unrelated condition or after the incidental discovery of raised serum alkaline phosphatase.o When patients does present, they present because any of the three : -Pain : - Dull constant acheDeformities : - Bowing of long bones, platybasia.Complications of the disease Complications of Paget's diseaseo Following complications can occur in Paget's disease : -Fracture: Are common in weight bearing bonesCranial nerve compression : - May cause impaired vision, facial palsy, trigeminal neuralgia or deafness.Otosclerosis : - Another cause of deafness in Paget's disease.Spinal canal stenosis and nerve root compressionHigh output cardiac failureOsteoarthritis : of Hip and kneeRarely osteosarcoma