Paget’s DiseaseDz

Synonyms: Osteitis deformans.

ICD-9 Code: 731.0.

ICD-10 Code: M88

Definition: Paget’s disease is a focal bone disorder in which the bone turnover rate is increased. It can affect single bones or multiple bones simultaneously.

Etiology: No cause is known, although a viral etiology has been postulated.

Pathology: In the earliest stage, increased bone resorption produces a purely lytic picture. This is followed by an intermediate stage in which active bone resorption and new bone formation (reactive sclerosis) occur in close proximity. Bony trabeculae may show thickening. Late in the disease, static sclerotic bony changes occur without further remodeling.

Demographics: The prevalence of Paget’s disease is ~3% in those older than age 40. Studies have suggested a higher prevalence in more temperate climates.

Cardinal Findings: With the widespread use of automated laboratory test profiles, Paget’s disease in most patients is detected in the asymptomatic stage by the finding of an elevated alkaline phosphatase. Bone pain and deformities can occur, distribution of which depends on the specific skeletal elements that are involved. Pain is described as deep, constant, and worse at night and may be aggravated by heat. Deformities include elongation of the long bones, causing bowing of the legs. The skull may also increase in size with resultant frontal bossing. Unstable pagetic bone may result in pathologic fractures after minimal trauma.

Uncommon Findings: Because of the high blood flow through newly formed bone, skin overlying the affected area may be warm. In severe cases, heart failure or decreased mentation may occur because of the high-output state. Hearing loss or vertigo may accompany impingement on the eighth cranial nerve. There is a small increased risk of giant cell tumors and osteogenic sarcoma.

Diagnostic Tests: Elevated alkaline phosphatase level suggests the diagnosis. Urinary excretion of hydroxyproline is increased and may be useful in following disease activity (Table 29). Bone biopsy is rarely indicated to exclude the presence of bone tumor.

Imaging: If bone pain is present, radiographs of these areas may be diagnostic. Long bones show the various stages of the disease from osteolysis to excessive bone formation. Thickening of the cranial bones may be seen on a skull film. Because the lumbar spine and sacrum are commonly affected, radio- graphs of these sites may be useful even in the absence of symptoms. Ra- dionuclide bone scanning helps to determine the extent of skeletal involve- ment.

Differential Diagnosis: Some of the lytic lesions may suggest metastatic disease. Bony changes associated with hyperparathyroidism might be considered, but in Paget’s disease the serum calcium levels are usually normal.

Therapy: Asymptomatic patients require no treatment. Bony pain, spinal involvement, deformities, or uncomfortable warmth are indications for medical therapy. Bisphosphonates (e.g., etidronate, alendronate, and pamidronate) are useful in reducing bone turnover and exert relatively long-lasting effects. Hyperphosphatemia is a possible side effect that can be corrected by lowering the dose. Bisphosphonates must be taken on an empty stomach to facilitate absorption. Calcitonin, another useful agent, is available as a nasal spray. Pain control may be better with calcitonin than with diphosphonates, but the effects of this agent are short-lived. Thus, flares are more frequent when the drug is stopped.

Surgery: Correction of deformities, including total joint replacements, appears to have the same success rate as in patients without Paget’s disease.

Prognosis: Medications that alter the disease course make cures possible in some patients.

BIBLIOGRAPHY

Hamdy RC. Clinical features and pharmacologic treatment of Paget’s disease. Endocrinol Metab Clin North Am 1995;24:421–433.PMID:7656897

Kanis JA. Treatment of Paget’s disease-an overview. Semin Arthritis Rheum 1994;23:254–255.PMID:8009244

Klein RM, Norman A. Diagnostic procedures for Paget’s disease: radiologic, pathologic, and laboratory testing. Endocrinol Metab Clin North Am 1995;24:437–449.