Octogenarian With Low Back Pain and an Enlarged Skull

An 81-year-old woman is hospitalized with localized nonradiating low back pain of 3 weeks' duration. She has no history of trauma, weakness of the legs, or urinary or bowel incontinence. The patient is alert and oriented to time, place, and person. Pulse rate is 88 beats per minute; blood pressure, 152/94 mm Hg; and respiration rate, 22 breaths per minute. The skull is enlarged with frontal prominence (Figure 1). No other bony deformity is demonstrated. Heart sounds are normal; rhythm is irregularly irregular. Bibasal crepitations but no rhonchi are noted. Abdominal findings are within normal limits. A Weber test demonstrates sensorineural deafness in the left ear, with no other focal neurologic deficit. Results of the straight-leg-raising test are normal. Tenderness is present in the T12-L1 region of the spine. Breast examination findings are normal. Paget disease of bone is strongly suspected as the cause of the patient's low back pain and left sensorineural deafness. To confirm Paget disease and rule out other causes of back pain, laboratory and imaging studies are ordered. The patient's alkaline phosphatase (ALP) level is 734 U/L (normal, 30 to 120 U/L); calcium and phosphorus levels are normal. A skull film reveals a "cotton wool" appearance that indicates disruption of normal bone architecture; in addition, the lucency in the calvaria heightens the suspicion of sarcomatous degeneration of the pagetoid skull (Figure 2). Lumbosacral films show increased density at T12 with mild trabecular thickening. A bone scan performed with intravenously administered technetium-labeled methylene diphosphonate demonstrates increased uptake ("hot spots") in the calvaria, T12, and left iliac crest (Figure 3).¹ These findings confirm the diagnosis of Paget disease of bone. The patient was given alendronate (40 mg once daily for 6 months); within 3 months, significant clinical and biochemical improvement was achieved. The low back pain resolved, and the ALP level normalized. The patient's sensorineural deafness remained. She refused surgical intervention for nerve compression.

PATHOGENESIS

Paget disease of bone, or osteitis deformans-a focal skeletal disorder that is characterized by an accelerated rate of bone turnover-causes both excessive resorption and excessive formation of bone.² The incidence of the disorder increases with age; both sexes are equally affected.³ The cause is unknown; however, studies suggest that genetic factors and/or viral infection may have a role.^4-6 Paramyxoviridae organisms have been isolated from osteoclasts of patients with Paget disease.⁷

PRESENTATION

Most patients with Paget disease are asymptomatic; frequently, the diagnosis is made incidentally during radiographic or laboratory investigation of other complaints. Microfractures or fissure fractures seen on x-ray films can suggest Paget disease. The signs and symptoms vary according to the site and extent of bone involvement. Bone pain, headaches that result from skull involvement, loss of hearing or vision from pressure on nerves, and bony deformity of affected areas are the major clinical manifestations.

WORKUP

Consider Paget disease of bone in the differential diagnosis of any elderly patient with symptomatic bone pain. Include in the evaluation a careful history, thorough physical examination, and measurement of serum biochemical markers. Serum calcium and phosphorus levels are normal in most patients with Paget disease. Serum ALP and urinary hydroxyproline levels are useful markers of disease activity, extent, and severity.⁸ Because of its high sensitivity and specificity, urinary pyridinium cross-link pyridinoline is increasingly used to monitor the response to therapy.⁹ Obtain x-ray films of affected areas to detect characteristic distortion of the bone architecture. A radionuclide bone scan is the most sensitive test for identifying pagetic bone lesions. In this patient, the bone scan revealed the “hot spot” at T12, which was the cause of her back pain.

COMPLICATIONS

Traumatic and pathologic fractures are common complications of pagetic lesions. Paget disease most often involves the axial skeleton, particularly the pelvic bone; however, any bony part of the body can be affected. In the leg, femoral fractures are more common than tibial fractures. In the upper limb, the humerus is involved more often than forearm bones. Neurologic complications can result from nerve compression caused by enlarging bone. In the skull, cranial nerves II, V, VII, and VIII may be affected; this can lead to optic, trigeminal, facial, and acoustic disorders. Rarely, in patients with widespread Paget disease and extensive hypervascularization of the bone marrow, an arteriovenous shunt can lead to high-output cardiac failure. Osteoarthritis can develop in patients whose pagetic bone is located near a joint. Unlike those who have osteoarthritis alone, patients with Paget disease experience increased pain with rest.

TREATMENT

Therapy is indicated for patients who have persistent pain in involved bones, neural compression, rapidly progressive bony deformity, fracture, or high-output cardiac failure. Cyclooxygenase-2 inhibitors or acetaminophen may ameliorate mild pain. Second-generation bisphosphonates, such as alendronate, are the mainstay of treatment; these agents can prevent disease progression and may limit complications.

References:

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