|
Paget’s disease of bone |
|
Epidemiology In the UK up to 3% of people over 40 years of age may have radiographic signs of Paget’s disease, although clinical disease is less common.
Aetiology The cause of Paget’s disease is unknown. There may be a genetic factor to the disease. Intranuclear inclusions compatible with a paramyxo– or other viruses have been demonstrated in both osteoblasts and osteoclasts.
Signs and symptoms The most commonly affected bones are the sacrum, spine, skull, femora and pelvis. The disease may be widespread and usually presents in a symmetrical pattern, but sometimes just a single bone is affected.
When the jaws are affected the alveolar process becomes symmetrically and grossly enlarged. There may also be gross and irregular hypercementosis of teeth, which show fusion to sclerotic areas of bone. Extraction of these teeth results in the tearing of segments of bone. Severe bleeding or osteomyelitis of ischaemic bone may follow.
Radiographic The main radiographic features are lower density of the bone in the early stages and sclerosis in later stages. These changes have a patchy, cotton-wool appearance.
Pathology Bone resorption and replacement becomes rapid, irregular, exaggerated and purposeless. The changes are erratic, and lead to thickening of affected bones without localised swellings. Initially this is seen as resorption, and later sclerosis is prominent. As different parts of the bone are affected at different stages the appearance is one of patchiness.
The changes in bony activity is seen histologically by an irregular pattern, giving a ‘mosaic’ appearance. Many osteoblasts and osteoclasts are seen and theses are often abnormally large. Fibrosis of the marrow spaces and increased vascularity results in bones becoming thickened and the cortex and medulla are obliterated. The whole bone is spongy in texture.
Complications The development of osteosarcoma is a rare complication of Paget’s. This virtually never presents in the jaws. Many patients live to an advanced age, despite their disabilities.
Treatment ¨ Calcitonin—by injection. Used to manage bone pain and osteolysis and to reduce bleeding from highly vascular bone. ¨ Bisphosphonates—depress bone turnover by slowing both the dissolution and growth of hydroxyapatite crystals. |
