Adverse events of treatment with rituximab in patients with myositis

Dear Editor, Rituximab and its biosimilars have been used to treat autoimmune rheumatic diseases for just over 20 years. It is of interest that these partially humanized monoclonal antibodies seem to induce biological responses/side effects at different rates in different diseases. A classification utilizing a different approach to diagnosis and management of each reaction has been reported [1]. Thus, in patients with rheumatoid arthritis, allergic responses were reported in about 22.6% of the patients [2]. These were mild (three patients developed rash and itching, two others had mild laryngospasm, one had chest heaviness with non-specific ECG changes and the last one had a bronchospasm) and they appeared not to be related to the immunosuppressant drug given in addition to the biosimilar, the infusion rate or the total amount of drug administered. In contrast, in the largest clinical assessment of which we are aware, in patients with systemic lupus erythematosus, we have reported infusion reactions in 17.6% of patients and 5.8% of total infusions [3]. We wondered where on this spectrum patients with myositis treated with rituximab were to be found.