A 75-year-old woman has experienced increasing dull but constant pain in the back, right chest, left shoulder and left upper thigh for the past 6 months. She has now developed a sudden, severe, sharp pain in the left thigh. On physical examination, she has intense pain on palpation of the upper thigh, and the left leg is shorter than the right. A radiograph of the left leg shows a fracture through the upper diaphyseal region of the femur in a 5-cm lytic area that extends through the entire thickness of the bone. A bone scan shows multiple areas of increased uptake in the left femur, pelvis, vertebrae, right third and fourth ribs, upper left humerus, and left scapula. Laboratory studies show serum creatinine, 0.9 mg/ dL; total protein, 6.7 g/dL; albumin, 4.5 g/dL; total bilirubin, 1 mg/dL; AST, 28 U/L; ALT, 22 U/L; and alkaline phosphatase, 202 U/L. What is the most likely diagnosis?

An elevated alkaline phosphatase level in an older adult should raise the suspicion of bone metastases, particularly when there is a "pathologic" fracture resulting from a bone lesion, rather than a fracture from trauma. Likely primary sites include the breast (in women), prostate (in men), lung (in smokers), kidney, and thyroid. Hyperparathyroidism can lead to osteitis fibrosa cystica with lytic lesions that are usually small, involve just the cortex, and appear first in phalanges. Multiple myeloma can produce lytic bone lesions, but the patient's serum gamma globulin level is not elevated. Osteochondromas are exostoses and do not produce lytic bone lesions. Paget disease of bone is characterized by osteolysis coupled with bone formation but without lytic lesions. Fibrous dysplasia coupled with cafe-au-lait spots on the skin and with endocrinopathies is known as McCune-Albright syndrome; this is a rare condition that occurs in young girls.