Abstract
Rheumatologists increasingly receive consults for patients treated with immune checkpoint inhibitors (ICIs) for cancer. ICIs can cause inflammatory syndromes known as immune-related adverse events (IRAEs). Several rheumatic IRAEs have been reported, including inflammatory arthritis, polymyalgia rheumatica, and myositis. For patients who present with musculoskeletal symptoms while receiving ICI therapy, it is important to have an algorithm for evaluation. The differential diagnosis includes a range of musculoskeletal syndromes, such as crystalline arthritis, mechanical issues, and osteoarthritis, in addition to IRAEs. After diagnosing a rheumatic IRAE, rheumatologists must work with the patient and the oncologist to form a treatment plan. Treatment of IRAEs is guided by severity. Evidence for management is limited to observational studies. Inflammatory arthritis and polymyalgia rheumatica are treated with nonsteroidal antiinflammatory drugs in mild cases, glucocorticoids for moderate-to-severe cases, and sometimes require other disease-modifying antirheumatic drugs. Myositis due to ICIs can be accompanied by myocarditis or myasthenia gravis. Glucocorticoids and withholding the ICI are usually required to treat myositis; some patients with severe myositis require intravenous immunoglobulin or plasmapheresis. Further research is needed to optimize treatment of IRAEs that does not compromise the antitumor effect of ICIs.