Dhora Gjoni
Oral Pathology
Den 2311/8243
Dr. Gwen Cohen Brown
Paget’s disease of bone
Paget’s disease of bone (PDB) is a condition that involves accelerated bone resorption followed by the deposition of dense and disorganized bone matrix. The cause of this disease is unknown, but genetic, inflammatory and endocrine factors may be the contributing agents. Moreover, studies over the last two or three decades have suggested that Paramyxovirus which can cause a slow viral infection, may also play a role in the etiology of this disease.
PDB rarely occurs before middle age. It normally affects the elderly, and there is a distinct geographical variation in the prevalence of the disease. According to epidemiological studies, PDB is more common in the United Kingdom and rare in Australia, North America and Western Europe. Men are affected more often than women and whites more frequently than blacks. Since it is often asymptomatic, PDB is frequently discovered in radiographs taken for other reasons, or from unexpected increase in serum alkaline phosphate. Even though most of the patients would remain asymptomatic, 5% of patients experience symptoms including:
· Bone and joint pain (occurring in the affected bone)
· Bone deformities that may result in the bowing of the limbs, described also as a simian (monkeylike) stance
· Increased skull size
· Fractures, since Pagetic bone is weaker than normal bone
· Hearing loss due to compression of the 8th cranial nerve
Pagetic lesions may be found in only one bone (monostotic) predominantly the pelvis, spine, skull and long bones or in multiple bones (polyostotic) which is generally more symptomatic. The affected bones become thickened, enlarged and weakened. Jaw involvement is present in approximately 17% of patients diagnosed with Paget’s disease. Maxilla gets affected far more common than the mandible. As a result, an enlargement of the middle third of the face is noted. The enlargement causes spacing of the teeth, if the patient is dentulous. Edentulous patients may complain that their dentures no longer fit because of their increased alveolar size. PDB has characteristic features on X-ray which usually do not leave the diagnosis in doubt, but the differential diagnosis may include other diseases. Radiographically, the early stages of Page’s disease reveal a decreased radiodensity of the bone and alteration of the trabecular pattern.
Large Circumscribed areas of radiolucency may be present, particularly in the skull. During the osteoblastic phase of the disease, patchy areas of sclerotic bone are formed that merge together. The patchy sclerotic areas are often described as having a “cotton wool” appearance. On radiographic examination the teeth often demonstrate extensive hypercementosis. Radiographic findings of PDB may resemble those of cement-osseous dysplasia. Patients with presumed cement-osseous dysplasia who demonstrate clinical expansion of the jaws should be evaluated to rule out PDB.
Microscopic examination shows an increase in bone resorption. Large osteoclasts surround bone trabeculae and show evidence of resorptive activity. At the same time, osteoplastic activity is also seen with disorganized bone formation. The bone formed is fragile and prone to facture, because of its altered bone quality.
Patients with Paget’s disease usually have normal blood calcium and phosphorus levels, but they show high elevations in serum alkaline phosphatase levels which is considered the most sensitive marker of bone formation. However, because serum alkaline phosphatase may also be elevated in other conditions other findings are needed to confirm the diagnosis. Clinical and radiographic features, combined with supportive laboratory findings are typically sufficient for diagnosis. Bone biopsy may be useful, but is rarely required in diagnosing PDB.
Although PDB is chronic and slowly progressive it is seldom the cause of death. Treatment is often not required for patient with limited involvement and no symptoms. The pain can be controlled with acetaminophen or NSAIDs. In asymptomatic patients systemic therapy is usually not initiated unless the alkaline phosphatase is more than 25% to 50% above normal. Drug management is mainly the therapy for active PDB. Bisphosphonates have become the gold standard for treatment of PDB. Bisphosphonates are antiresorptive medicines. They slow or stop the natural process that dissolves bone tissue, resulting in maintained or increased bone density and strength. Other antiresorptive therapy may be considered for patients who are intolerant or nonresponsive to bisphosphonates. In mild cases, a single infusion of Bisphosphonates is associated with yearlong remission. Patient with more severe disease usually require higher doses or more frequent courses of a particular Bisphosphonates. The goal of the therapy is to archive midrange normal levels of serum alkaline phosphatase with retreatment occurring when values rise 25% or higher than normal. Surgery is also a treatment to manage fractures and deformity in patient with active PDB. Since Pagetic bone is very vascular, there is an increased risk of blood loss. Therefore, the administration of Bisphosphonates therapy prior to surgery is recommended. ONJ (Osteonecrosis of the jaw) is a rare complication that affects a small number of people who are treated with Bisphosphonates. Long time data are needed to fully evaluate the potential risks and benefits of Bisphosphonate therapy. For this reason, aggressive treatment of PDB remains unsure at this time. Another recognized complication of PDB, is the development of a malignant bone tumor known as Osteosarcoma. Most of the Osteosarcomas develop in the pelvis, and long bones of the lower extremities. The skull and the jaw are very rare sites for this type of malignancy. Osteosarcomas in PDB are very aggressive and associated with poor prognosis.
Dental hygienists should be aware of the signs and symptoms of PDB and possible complications that would interfere with dental treatments. Early detections of malignancies and the ONJ (osteonecrosis of the jaw) are very critical. Some of the symptoms that a dental patient might experience when ONJ is suspected include pain, numbness or a heaviness of the jaw, gum infections and loosening of teeth. In addition, dentures and implants would not be the best treatments for these patients because, Pagetic bone is always changing. Therefore, maintaining a good oral hygiene and getting regular dental care is very important for these patients.
References:
1. Josse, MB, Robert G, David A Hanley,MD, et al, et al, et al, and Jacques Brown,MD. “Diagnosis and treatment of Paget’s disease of bone.” Position Paper. Vol 30.no5 (2007): n. page. Print.
2. Neville, B. W., D. D. Damm, and C. M. Allen. Oral and maxillofacial pathology. 3rd. Saunders, 2009. 623-626. Print.
