Using B-cell-targeting drugs to achieve marked efficacy in anti-signal recognition particle myopathy: two case reports.

Anti-signal recognition particle (anti-SRP) antibody-associated myopathy is a severe immune-mediated necrotizing myopathy characterized by elevated serum creatine kinase (CK), rapidly progressive proximal weakness, and specific pathological features on muscle biopsy. Cardiac involvement and even paralysis may occur in some patients. Response to steroid monotherapy and conventional immunosuppressants is often suboptimal, whereas B-cell-targeted therapies represent the potential advantages. We report two patients with anti-SRP myopathy treated with B-cell-targeted drugs individually. One achieved remission with low-dose rituximab (RTX), and the other responded to telitacicept (RC-18) at the lowest effective dose. During follow-up, both patients improved substantially and maintained long-term remission without relapse or infection. These cases support the feasibility of individualized B-cell-targeted strategies, including low-dose RTX and RC-18, for anti-SRP myopathy. Given the limited evidence, prospective studies are needed to assess the efficacy and safety.