Signs and Symptoms
- Paget's disease is often asymptomatic in mild or early cases
- The most common symptom is bone pain
- Symptoms may be confused with arthritis or other disorders
- Increasing deformity of bones may be noticed
- Skull involvement may cause frontal bossing, increased hat size, and headaches

Associated Conditions
- Paget's disease can lead to osteoarthritis due to changes in bone shape
- Severe Paget's disease may result in heart failure
- Kidney stones are more common in patients with Paget's disease
- Nervous system problems can occur due to increased pressure on the brain or spinal cord
- Facial bone involvement may cause loose teeth and chewing difficulties

Causes
- Paget's disease may be caused by a slow virus infection
- Viral infections associated with Paget's disease include respiratory syncytial virus, canine distemper virus, and measles virus
- Genetic factors play a role in the development of Paget's disease
- Mutations in genes SQSTM1 and RANK are associated with Paget's disease
- About 40-50% of people with inherited Paget's disease have a mutation in the SQSTM1 gene

Pathogenesis and Treatment
- Paget's disease progresses through four stages: osteoclastic activity, mixed osteoclastic-osteoblastic activity, osteoblastic activity, and malignant degeneration
- Initially, there is increased bone resorption caused by osteoclasts
- This is followed by compensatory bone formation by osteoblasts
- The bone formation is disorganised, resulting in a mosaic pattern
- The bone becomes hypervascular and may eventually become dense or 'burned-out'
- There is no cure for Paget's disease, but medications can help control symptoms
- Bisphosphonates and calcitonin are commonly used medications for Paget's disease
- Treatment is more successful when started early before complications arise

Diagnosis, Medication, Surgery, and Specialists
- Elevated alkaline phosphatase in the blood is the first clinical manifestation
- Pagetic bone has a characteristic appearance on X-rays
- Urine markers of bone turnover, such as pyridinoline, can be used
- Elevated levels of serum and urinary hydroxyproline are found
- Bone scans can determine the extent and activity of the condition
- Medications are recommended for those with bone pain, elevated alkaline phosphatase levels, or risk of bone fracture
- Bisphosphonates like risedronic acid, alendronic acid, and pamidronic acid are commonly prescribed
- Neridronate and etidronate disodium are also used, with specific dosing regimens
- Zoledronic acid is given as an intravenous infusion and is effective for two years
- Surgery may be recommended for fractures, severe degenerative arthritis, and bone deformity
- Fractures may heal in a better position with surgery
- Joint replacement of hips and knees may be considered for severe arthritis
- Osteotomy, cutting and realignment of pagetic bone, can help with painful weight-bearing joints
- Endocrinologists, rheumatologists, orthopedic surgeons, neurosurgeons, neurologists, oral and maxillofacial surgeons, and otolaryngologists are knowledgeable about treating Paget's disease
- Various specialists may be involved in the ongoing management and treatment of the disease.