Paget's disease of bone (commonly known as Paget's disease or, historically, osteitis deformans) is a condition involving cellular remodeling and deformity of one or more bones. The affected bones show signs of dysregulated bone remodeling at the microscopic level, specifically excessive bone breakdown and subsequent disorganized new bone formation.[1] These structural changes cause the bone to weaken, which may result in deformity, pain, fracture or arthritis of associated joints.[1]

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Wiki: Paget disease of bone