Mycophenolate mofetil as salvage therapy for refractory acute-onset CIDP associated with rheumatoid arthritis: a case report.

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an immune-mediated neuropathy that rarely co-occurs with rheumatoid arthritis (RA). When CIDP proves refractory to first-line therapies, management becomes particularly challenging, especially in patients with multiple autoimmune conditions. A 43-year-old Chinese male with a 3-year history of seropositive RA in sustained remission presented with acute progressive quadriparesis, bilateral ptosis, and facial diplegia. Cerebrospinal fluid analysis revealed albuminocytologic dissociation, and nerve conduction studies demonstrated evolving demyelinating features, consistent with a diagnosis of acute-onset CIDP (A-CIDP). The patient responded inadequately to sequential treatment with intravenous immunoglobulin, high-dose corticosteroids, and the neonatal Fc receptor (FcRn) antagonist efgartigimod, experiencing repeated relapses during corticosteroid tapering. Mycophenolate mofetil (MMF) was subsequently introduced as a steroid-sparing agent at 0.75 g twice daily, enabling further prednisone tapering from 20 mg to 10 mg daily without relapse; MMF was later up-titrated to 1 g twice daily. Under a combined, multi-target immunosuppressive regimen of MMF, prednisone, methotrexate, iguratimod, and hydroxychloroquine, the patient achieved sustained neurological improvement, with prednisone successfully tapered to 10 mg daily by October 2025 and maintained thereafter. By April 2026, only residual mild ptosis persisted, and no infectious complications occurred. This case suggests that MMF-based multi-target immunosuppression may be a therapeutic option for RA-associated, treatment-refractory A-CIDP, potentially enabling successful glucocorticoid tapering even after an inadequate response to a short course of FcRn-targeted therapy.