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Paget's disease is characterized by abnormal bone remodeling, leading to the enlargement and weakening of bones. In this condition, although calcium and phosphate levels may remain within the normal range, alkaline phosphatase, an enzyme linked to bone formation, is elevated. This increase in alkaline phosphatase arises due to the heightened osteoblastic activity associated with the extensive bone remodeling that defines Paget's disease.

In contrast, osteoporosis typically presents with low bone mass and structural deterioration but does not involve a significant increase in alkaline phosphatase. Rickets and osteomalacia are both caused by vitamin D deficiency or abnormalities in calcium and phosphate metabolism and are associated with low calcium or phosphate levels, which would not match the criteria provided in this scenario. Therefore, the distinctive presentation of high alkaline phosphatase alongside normal calcium and phosphate is specific to Paget's disease, making it the correct answer.