TRANSIENT OSTEOPOROSIS: CLINICAL SPECTRUM IN ADULTS AND ASSOCIATED RISK FACTORS

We aimed to describe the natural history of the rare clinical syndrome of transient osteoporosis (TO) and ascertain potential risk factors. Retrospective cohort study of adults with TO at Mayo Clinic, Rochester, Minnesota, over 15 years. Adults with acute-onset joint pain worsened by weight bearing and bone marrow edema on magnetic resonance imaging were included; exclusion criteria were trauma, tumors, rheumatic diseases, avascular necrosis, infection, and hyperesthesia. Thirty-three patients with TO were identified: 20 males, median age at diagnosis 47 years, and median body mass index 28 kg/m². Median time to diagnosis was 2 months, and time to symptom resolution was 4 months. All cases involved the lower extremity, with the majority affecting the hip. Most patients (79%) had at least one possible identified risk factor. The most frequent risk factor was low bone mineral density (BMD) in 13 patients (39% of cohort). Of the 16 patients with BMD measure, 8 had low BMD at a site other than TO. The next most frequent risk factors were sudden limb overuse and more than one episode of TO, observed in 30%, followed by a disorder of bone and mineral metabolism in 27%. TO affects middle-age men more than women, primarily involves weight-bearing joints, and usually resolves with conservative management. Its etiology remains unclear; however, the common presence of risk factors, abnormalities in bone and mineral laboratories, and decrease in BMD suggest that systemic factors may be important in its development. Abbreviations: AVN = avascular necrosis; BMD = bone mineral density; DXA = dual-energy X-ray absorptiometry; MRI = magnetic resonance imaging; TO = transient osteoporosis.