A 60-year-old man comes to the office due to a 6-month history of constant back pain, thigh pain, and headache. He has moderate, deep, achy pain in the mid lumbar area that does not radiate and is worse with changes in position such as rolling over in bed. The patient has no significant history of trauma, and the course of his symptoms has been stable but persistent. He has been taking acetaminophen without relief. There is no associated nausea, vomiting, weight loss, fever, difficulty walking, leg numbness, or urinary symptoms. Medical history is notable for hypertension treated with chlorthalidone and lisinopril. He also uses a hearing aid for recently acquired, left-sided hearing loss. Blood pressure is 138/85 mm Hg, pulse is 76/min, and respirations are 12/min. BMI is 29 kg/m². The patient appears comfortable and in no acute distress. Cardiopulmonary examination is normal. The abdomen is soft and nontender with no organomegaly. He has mild thoracic dextroscoliosis and a decrease in the normal lumbar lordosis. The lower extremities show mild anterolateral femoral bowing. Upper and lower motor strength, sensation, and reflexes are normal. Which of the following is the most likely cause of this patient's current condition?

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11ec25c8_d513_9522_bc81_23b1d6314dde_MD0003_00 This patient with bone pain, headaches, unilateral hearing loss, and femoral bowing has typical symptoms of Paget disease of bone. Paget disease is the most common bone disorder after osteoporosis, affecting approximately 3% of adults age >40. It is characterized by a focal increase in bone turnover, in which osteoclast dysfunction leads to bone breakdown and a compensatory increase in bone formation. The pelvis, skull, spine, and long bones are most commonly involved. Microscopic findings include increased numbers of abnormal-appearing osteoclasts, with a disorganized "mosaic" pattern of lamellar bone. Early-stage lesions will have a predominance of osteoclast activity, later progressing through a mixed osteoclastic/osteoblastic phase, a predominantly osteoblastic phase, and a residual sclerotic phase. Most patients with Paget disease are asymptomatic and are identified incidentally by radiographic findings or elevated alkaline phosphatase levels. Symptoms may include skeletal deformities, bone or joint pain, and fractures. Enlarging cranial bones may lead to increased hat size, headaches, and hearing loss due to entrapment of cranial nerve VIII or encroachment on the cochlea. Additional complications include benign giant cell tumors of bone and osteosarcoma. (Choice A) Osteomalacia due to malabsorption of calcium and vitamin D causes abnormal mineralization of bone with muscular weakness, bone pain, and deformity. However, it would not lead to unilateral hearing loss, and this patient has no history of a malabsorptive disorder (eg, celiac disease). (Choice B) Glucocorticoids can cause osteoporosis, in part due to induction of apoptosis in osteoblasts. Osteoblast activity is increased in Paget disease. (Choice D) Hyperparathyroidism can present with weakness, abdominal pain, and bone pain or fractures. Hearing loss would not be seen. (Choice E) Multiple myeloma (a plasma cell dyscrasia) can cause osteolytic lesions, osteoporosis, and fractures. However, bowing, unilateral hearing loss, and absence of systemic symptoms are more typical of Paget disease. (Choice F) Overproduction of calcitriol (the active form of vitamin D) is seen in granulomatous diseases such as sarcoidosis and tuberculosis. Hypercalciuria and hypercalcemia may occur, leading to kidney stones, nephrocalcinosis, and renal failure. Educational objective: Paget disease of bone is characterized by osteoclast dysfunction with a focal increase in bone turnover. Most patients are asymptomatic, but symptoms may include skeletal deformities, bone pain, and fractures. Involvement of cranial bones may lead to headaches and hearing loss.

A 60-Year-Old Man Comes to the Office Due to a 6-Month