musculoskeletal and connective tissue disorders
Paget Disease of Bone
Diagnosis of Paget Disease of Bone
Plain x-rays Elevated serum alkaline phosphatase or other markers of increased bone turnover Bone scan to establish the extent and location of disease Paget disease should be suspected in patients with the following: Unexplained bone pain or deformity Suggestive findings on x-ray Unexplained elevation of serum alkaline phosphatase on laboratory tests done for other reasons, particularly if liver-sourced 5'-nucleotidase or gamma-glutamyl-transpeptidase (GGT) is normal If Paget disease is suspected, plain x-rays and serum alkaline phosphatase, 25OH-vitamin D, creatinine, calcium, and phosphate levels should be obtained. Characteristic laboratory findings include elevated serum alkaline phosphatase (increased anabolic activity of bone) but usually normal serum gamma-glutamyl-transpeptidase (GGT), 5'-nucleotidase, and serum phosphate levels. Serum calcium is usually normal, though in the setting of immobilization may be increased. If hypercalcemia is present, the patient should be evaluated for concurrent hyperparathyroidism. If alkaline phosphatase is not elevated or it is unclear whether the increased serum alkaline phosphatase is of bony origin (ie, if GGT is increased in proportion to alkaline phosphatase), a bone-specific alkaline phosphatase fraction can be measured. Serum markers of bone turnover, such as procollagen type I intact N-terminal propeptide (PINP) and C-telopeptide cross-links (CTX), may be elevated. A 25OH-vitamin Dlevel and creatinine should be checked before treating symptomatic patients with bisphosphonates. Confirmation on x-ray is required to establish the diagnosis. Characteristic x-ray findings include abnormal architecture with coarse trabeculae and cortical thickening and sclerosis. Involved bone may be enlarged, and pagetic lesions in the tibia or femur may result in bowing. Once a diagnosis of Paget's disease of bone is made on x-ray, a radionuclide bone scan using technetium-labeled phosphonates should be done to determine the extent of bone involvement. However, in cases of diagnostic uncertainty, a biopsy should be performed to exclude possible metastatic disease. A biopsy is also indicated for patients with known pagetic bone involvement who have worsening symptoms at the affected site to evaluate for osteosarcoma or other tumors (eg, giant cell tumor of bone). Consider Paget disease of bone in older adults with elevated alkaline phosphatase but normal GGT levels. 