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Emergency and Acute Medicine – Paget Disease
Paget disease, also known as osteitis deformans, is a disorder of bone remodeling characterized by excessive resorption of normal bone followed by replacement with disorganized, fibrous, and sclerotic bone. The disease is usually focal and most commonly affects the pelvis, femur, skull, tibia, and spine, particularly the lumbar spine. It occurs in approximately 1–2% of individuals older than 55 years, with incidence increasing with age. Many patients are asymptomatic, and the disease is often discovered incidentally on radiographs or through elevated alkaline phosphatase levels.
The disease begins with an osteolytic phase in which osteoclasts aggressively resorb healthy bone. This phase is associated with increased bone vascularity, predisposing patients to hematoma formation and pathologic fractures. Over time, the resorbed bone is replaced by dense, irregular trabecular bone in the osteoplastic phase, forming a characteristic mosaic pattern. Although malignant transformation is rare, occurring in about 1% of cases, osteosarcoma is the primary malignancy of concern. Paget disease is more common in men and individuals of European descent and is rare in children.
The etiology remains unclear, though both genetic and environmental factors are implicated. Mutations in the SQSTM1 gene have been identified in many cases, and viral inclusions seen in osteoclasts suggest a possible association with paramyxoviruses. Environmental factors such as rural living and exposure to farm animals may also contribute.
Clinical presentation varies widely. Many patients remain asymptomatic, while others develop deep, aching bone pain later in the disease course. Pain may worsen with weight bearing when the femur or tibia is involved or with rest when non–weight-bearing bones are affected. During the acute osteolytic phase, patients are at risk for pathologic fractures, hypercalcemia, renal stones, and bleeding due to hypervascular bone. In widespread disease, increased bone blood flow may lead to high-output cardiac failure. In the osteoplastic phase, long-bone involvement can cause deformity, gait abnormalities, and swelling. Skull involvement may lead to headaches, cranial nerve compression, hearing loss, or changes in head size, while spinal disease can cause neurologic compression.
Diagnosis is usually suggested by characteristic radiographic findings and supported by laboratory abnormalities. Alkaline phosphatase is the most sensitive marker of disease activity, while calcium and phosphate levels are typically normal unless complications such as fracture or immobilization occur. Imaging with plain radiographs often reveals lytic lesions, bone expansion, cortical thickening, or dense “ivory” bone. Radionuclide bone scans are useful to assess the extent and activity of disease, while CT or MRI helps evaluate complications such as neoplasm, hematoma, or spinal cord compression.
Emergency management focuses on complications rather than the underlying disease. Pathologic fractures require prompt immobilization to limit bleeding, and analgesia is provided with acetaminophen or opioids. Hypercalcemia is treated with intravenous fluids, calcitonin, and bisphosphonates as needed. Suspected neurologic compromise mandates urgent neurosurgical consultation. Definitive medical therapy is indicated for symptomatic patients or those with disease in high-risk locations and typically involves nitrogen-containing bisphosphonates such as alendronate, risedronate, pamidronate, or zoledronic acid.
Admission is indicated for patients with major trauma, significant bleeding, hypercalcemia, high-output cardiac failure, or neurologic compression. Stable patients with adequate pain control and no acute complications may be discharged with appropriate orthopedic and endocrinology follow-up. A key clinical pearl is that Paget disease is often an incidental diagnosis, and unexplained elevation of alkaline phosphatase or pathologic fracture in an older adult should prompt consideration of this condition.
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