SLE is a relatively common chronic disorder of an inflammatory nature of unknown etiology. SLE affects multiple organ systems of the body including the skin, joints, entheses, kidneys, lungs, serous membranes, nervous system, and others. SLE may cause immunological changes and abnormalities, especially antinuclear antibodies. The clinical course is characterized by remission and acute relapse, and long-term steroid administration may result in osteoporosis, avascular necrosis, and microfractures, especially in the weight-bearing joints of the hips and knees. As in rheumatoid arthritis, articular involvement is multiple and symmetrical, but deformity is not a prominent feature unless complicated by osteonecrosis.
Radiographic changes include articular widening and periarticular soft-tissue swelling, and are observed more typically in steroid-naive patients. Although infrequent, articular narrowing, osteonecrosis, deformity, soft-tissue calcification, and acrosclerosis or acrolysis may be seen in patients with longstanding disease. Whole-body scintigraphy demonstrates sym-
Fig. 12.10A, B Admixture of "cold" and "hot" areas in SLE. A Anterior pinhole scintigraph of the right knee in a 25-year-old woman with SLE treated with steroid for 3 months shows multiple photon defect irregularly mixed with increased tracer uptake reflecting avascular necrosis and microfractures, respectively. B Anteroposterior radiograph is surprisingly normal
Fig. 12.11A-C SLE accompanied by hypertrophic osteoarthropathy. A Whole-body scan in a 24-year-old woman with steroid-treated SLE shows bone uptake in the hips and knees (arrows). B Composite anterior pinhole scan shows a mixture of photopenia in necrotized bones in the intercondylar region (open arrows) and diffusely increased uptake in hypertrophic osteoarthropathy in the distal femur (arrows). C Anteroposterior radiograph shows periosteal thickening in the distal femur (open arrows). Note that osteonecrosis and bone reaction are not visualized radiographically
metrical polyarthritis in the shoulders, elbows, hips, knees, and spine resembling classic rheumatoid arthritis (Fig. 12.9A). However, pinhole scintigraphy in relatively early or steroid-treated cases may reveal prominent tracer uptake that is peculiarly localized to the physes and metaphyses (Figs. 12.8B and 12.9B). Articular uptake may (Fig. 12.8B) or may not (Fig. 12.8B) coexist. The implication of such findings is not clear. In still other cases, the periarticular bone uptake is inhomogeneous with photopenic and photodense areas, probably representing avas-cular necrosis and microfractures, respectively (Fig. 12.10). Radiography may not be abnormal (Fig. 12.10B).
On occasion, SLE may become complicated with, in addition to osteonecrosis, hypertro-phic osteoarthropathy, and both can be diagnosed accurately using pinhole scanning. Whole-body scans show irregular uptake of osteonecrosis in the hips and knees (Fig. 12.11A), and magnified scans show osteonecrosis as photopenia and osteoarthropathy as characteristic cortical uptake (Fig. 12.11B). Although rare, SLE may involve the costovertebral and costotransverse joints of the thoracic spine (Fig. 12.12), giving rise to a "centipede" appearance that is also observed in ankylosing spondylitis (Fig. 11.6).
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