Also known as osteitis deformans, Paget’s disease is a slowly progressive metabolic bone disease characterized by an initial phase of excessive bone resorption (osteoclastic phase), followed by a reactive phase of excessive abnormal bone formation (osteoblastic phase). The new bone structure, which is chaotic, fragile, and weak, causes painful deformities of both external contour and internal structure.
Paget’s disease usually localizes in one or several areas of the skeleton (most commonly the lower torso); however, occasionally, skeletal deformity is widely distributed. It can be fatal, particularly when it’s associated with heart failure (widespread disease creates a continuous need for high cardiac output), bone sarcoma, or giant cell tumors.
Paget’s disease occurs worldwide but is more common in Europe, Australia, and New Zealand, where it’s seen in up to 5% of the elderly population.
Although its exact cause is unknown, one theory holds that early viral infection (possibly with mumps virus) causes a dormant skeletal infection that erupts many years later as Paget’s disease. In 5% of the patients, the involved bone will undergo malignant changes.
Clinical features of Paget’s disease vary.
A patient in the early stages of the disease may be asymptomatic; however, when pain develops, it’s usually severe and persistent and may coexist with impaired movement resulting from impingement of abnormal bone on the spinal cord or sensory nerve root. Such pain intensifies with weight bearing.
The patient with skull involvement shows characteristic cranial enlargement over frontal and occipital areas (hat size may increase) and may complain of headaches. Other deformities include kyphosis (spinal curvature due to compression fractures of vertebrae), accompanied by a barrel-shaped chest and asymmetrical bowing of the tibia and femur, which can reduce height. Pagetic sites are warm and tender and are susceptible to pathologic fractures after minor trauma. Pagetic fractures heal slowly, and for many patients they never completely heal.
Bony impingement on the cranial nerves may cause blindness and hearing loss with tinnitus and vertigo. Other complications include hypertension, renal calculi, hypercalcemia, gout, heart failure, and a waddling gait (from softening of pelvic bones).
X-rays taken before overt symptoms develop show increased bone expansion and density. A bone scan, which is more sensitive than an X-ray, clearly shows early pagetic lesions (radioisotope concentrate in areas of active disease). Bone biopsy reveals characteristic mosaic pattern. Other laboratory findings include:
❑ increased serum alkaline phosphatase (ALP) levels (an index of osteoblastic activity and bone formation)
❑ increased levels for markers of bone breakdown such as N-telopeptide
❑ increased 24-hour urine levels for hydroxyproline (amino acid excreted by the kidneys and an indicator of osteoclastic hyperactivity)
❑ increased or decreased serum calcium and ALP isoenzyme levels.
If the patient is asymptomatic, treatment isn’t needed. The patient with symptoms requires drug therapy, which may include:
❑ calcitonin (a hormone, given subcutaneously or I.M.) and etidronate (oral) to retard bone resorption (which relieves bone lesions) and reduce serum ALP and urinary hydroxyproline secretion. Although calcitonin requires long-term maintenance therapy, improvement is noticeable after the first few weeks of treatment; etidronate, a bisphosphonate, produces improvement after 1 to 3 months. Other bisphosphonates include alendronate, pamidronate, risedronate, and tiludronate.
❑ mithramycin, a cytotoxic antibiotic, to decrease urinary hydroxyproline and serum calcium, and ALP levels. This drug produces remission of symptoms within 2 weeks and biochemical improvement in 1 to 2 months. However, mithramycin may destroy platelets or compromise renal function.
Self-administration of calcitonin and etidronate helps patients with Paget’s disease lead near-normal lives. Nevertheless, these patients may need surgery to reduce or prevent pathologic fractures, correct secondary deformities, or relieve neurologic impairment.
To decrease the risk of excessive bleeding due to hypervascular bone, drug therapy with calcitonin and etidronate or mithramycin must precede surgery. Joint replacement is difficult because bonding material (methylmethacrylate) doesn’t set properly on pagetic bone.
Other treatments vary according to symptoms. Aspirin, indomethacin, or ibuprofen usually control pain.
❑ To evaluate the effectiveness of an analgesic, assess the patient’s pain level daily. Watch for new areas of pain or restricted movements — which may indicate new fracture sites — and sensory or motor disturbances, such as difficulty in hearing, seeing, or walking.
❑ Monitor serum calcium and ALP levels.
❑ If the patient is confined to prolonged bed rest, prevent pressure ulcers by providing good skin care. Reposition the patient frequently, and use a flotation mattress. Provide high-top sneakers to prevent footdrop.
❑ Monitor intake and output. Encourage adequate fluid intake to minimize renal calculi formation.
❑ Demonstrate how to inject calcitonin properly and rotate injection sites. Warn the patient that he may experience adverse reactions (nausea, vomiting, local inflammatory reaction at injection site, facial flushing, itching of hands, and fever). Reassure him that such reactions are usually mild and infrequent.
❑ To help the patient adjust to the changes in lifestyle imposed by this disease, teach him how to pace activities and, if necessary, how to use assistive devices.
❑ Encourage the patient to follow a recommended exercise program — avoiding immobilization and excessive activity. Suggest a firm mattress or a bed board to minimize spinal deformities.
❑ To prevent falls at home, advise the patient to remove throw rugs and other small obstacles.
❑ Emphasize the importance of regular checkups, including those for the eyes and ears.
CLINICAL TIP: Tell the patient receiving etidronate to take this medication with fruit juice 2 hours before or after meals (milk or other high-calcium fluids impair absorption), to divide the daily dosage to minimize adverse effects, and to watch for and report stomach cramps, diarrhea, fractures, and increasing or new bone pain.
❑ Tell the patient receiving mithramycin to watch for signs of infection, easy bruising, bleeding, and temperature elevation, and to report for regular follow-up laboratory tests.
❑ Help the patient and his family make use of community support resources, such as a visiting nurse or home health agency. For more information, refer them to the Paget’s Disease Foundation.
Review other book chapters online related to Paget's disease of bone:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2003 ISBN: 1-58255-266-5 
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