[Drug-induced osteopathy in rheumatology]

Osteopathy in rheumatology can either be primary a condition as a consequence of inflammatory rheumatic diseases but can also be drug induced. The most severe clinical manifestations are insufficiency fractures and osteonecrosis. The risk of fractures is highest for patients treated with glucocorticoids depending on the daily intake, the cumulative glucocorticoid dosage and the duration of administration. An incidence rate of nearly 13% was reported after administration of glucocorticoids lasting > 1 year. Cases of osteonecrosis under glucocorticoids are, in contrast, less frequent and not associated with glucocorticoid-induced osteoporosis. The antiresorptive substances bisphosphonates and denosumab, as well as romosumab are effective and important in treating osteoporosis; however, they can also cause atypical fractures, particularly of the femur as well as osteonecrosis of the jawbone. According to the most recent guidelines the benefits of bisphosphonate treatment have only been verified for 3-5 years and for denosumab for 3 years. There are clear preventive recommendations to avoid osteonecrosis of the jaw. Ultimately, the disease-modifying antirheumatic drugs (DMARD) methotrexate and leflunomide also affect the metabolism of bones. There is a rare but very characteristic form of osteopathy associated with methotrexate, mainly occurring in cases of long-term treatment. The typical manifestations are insufficiency fractures, particularly of the distal tibia, which persist for many years under continuous methotrexate administration. The treatment is the discontinuation of methotrexate and in most cases the fractures will heal within 3-4 months. Leflunomide has been associated with cases of persisting pseudarthrosis that only disappeared after a wash-out of the active metabolite.