Adult Paget's disease of bone: a review.

Adult PD of bone is the second commonest metabolic bone condition after osteoporosis. The condition is characterized by increased bone cell activity, with bone-resorbing osteoclasts often larger and containing more nuclei than normal, and osteoblasts producing increased amounts of disorganized bone. This leads to expanded bone of poor quality possessing both sclerotic and lytic areas. PD of bone has a strong genetic element, with a family history being noted in 10-20% of cases. A number of genetic defects have been found to be associated with the condition. The most common disease-associated variants identified affect the SQSTM1 gene, providing insights into disease aetiology, with the clinical value of knowledge of SQSTM1 mutation status currently under active investigation. The diagnosis may be suggested by an isolated raised total ALP without other identifiable causes. This can be confirmed on plain X-rays and the extent determined by isotope bone scan. The mainstays of treatment are the bisphosphonates, especially i.v. zoledronate, which results in long-term suppression of bone turnover. ALP is the usual means of monitoring the condition, although more specific bone turnover markers can be helpful, especially in coincident liver disease. Patients should be followed up to monitor for biochemical relapse or development of complications, which may require medical or surgical intervention.