[Successful Treatment of Rheumatoid Arthritis Complicated with Myasthenia Gravis with Low-dose Rituximab: A Case Report]

Rheumatoid arthritis (RA) and myasthenia gravis (MG) are two distinct autoimmune diseases. Compared with the general population, the incidence of RA is notably higher among patients with MG. Similarly, the rate of MG in patients diagnosed with RA is also significantly increased. In this report, we presented an elderly female patient with a history usage of long-term glucocorticoid and conventional synthetic disease-modifying antirheumatic drugs (csDMARDs), whose RA symptoms remained inadequately controlled. She later exhibited drooping of the right eyelid and double vision, leading to a diagnosis of ocular myasthenia gravis (OMG). Then, we made a literature review and found that the RA patients with co-existing MG were relatively more common in middle-aged and elderly women, and most of them did not have thymoma. Thymoma wasn ' t found in our patient, which was consistent with the cli-nical characteristics of RA complicated with MG reported in previous reports. In addition, there was li-mited treatment experience in patients with both RA and MG. The treatment stratergies for RA or MG included glucocorticoids and immunosuppressants. Among the 18 patients we analyzed, 8 patients expe-rienced relief after csDMARDs, while other 8 patients received biologics or targeted DMARDs, including tumor necrosis factor inhibitors (TNFi) in 5 cases, JAK inhibitors in 2 cases, and B-cell depletion therapy (rituximab) in 2 cases. What called for special attention was that one RA patient was diagnosed with MG after using 23 months of methotrexate and 6 weeks of etanercept (TNFi), with rituximab 1 000 mg for the first time, followed by 500 mg every 6 months, and finally both RA and MG were well controlled. For the patient in this study, MG symptoms improved with increased dosage of prednisone. In order to tapper the dose of glucocorticoid, it was necessary for more potent immunosuppressant for both RA and MG. Given her history of cardiac conditions, JAK inhibitors were not considered, and due to the uncertain efficacy of TNFi, we chose to administer low-dose rituximab (100 mg). Subsequent follow-up revealed stable conditions for both RA and MG, allowing for discontinuance of glucocorticoid after 5 months. It reflected the potential efficacy and cost-effectiveness of low-dose, long-interval rituximab in treating RA patients combined with MG, while it also minimized infection risks. However, the duration for subsequent infusions remained uncertain and required further observation. In conclusion, RA combined with MG is rare. For patients exhibiting poor responses to csDMARDs, low-dose, long-interval rituximab might be a promising treatment option.