Efgartigimod for acute attacks of brainstem MOGAD followed by mycophenolate mofetil maintenance: a case report

Abstract

Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is an autoimmune inflammatory demyelinating disorder of the central nervous system with a broad clinical spectrum that includes brainstem syndromes. Evidence supporting neonatal Fc receptor (FcRn) inhibition in MOGAD remains limited. A 37-year-old woman presented with a MOGAD-associated brainstem syndrome characterized by diplopia, ocular-motor abnormalities, right facial weakness, and gait instability. Brain MRI demonstrated a lesion in the right middle cerebellar peduncle near the fourth ventricle. CSF analysis showed 2 leukocytes/µL, 0 erythrocytes/µL, normal protein (0.328 g/L), a type II oligoclonal-band pattern, and an elevated IgG index of 1.8 (reference value, <0.7), supporting intrathecal IgG synthesis. Serum MOG-IgG was positive by live cell-based assay. High-dose corticosteroids were discussed, but the patient declined them because of concerns regarding adverse effects. IVIG was subject to intermittent local shortage and substantial financial burden, while PLEX was considered disproportionate to the clinical severity. The patient received individualized off-label intravenous efgartigimod (20 mg/kg on Days 1 and 5) and improved clinically. After the second relapse, the same efgartigimod regimen was repeated, and low-dose oral prednisone and MMF were initiated for relapse prevention. Prednisone was discontinued approximately 5 months after initiation, whereas MMF was continued as maintenance therapy. At follow-up approximately 18 months after discharge, the patient was clinically asymptomatic. This case documents a recognized brainstem MOGAD presentation with clinical improvement temporally associated with individualized off-label FcRn inhibition. Interpretation should consider the single-case design, absence of a comparator, rehabilitation, low-dose prednisone and MMF initiated for relapse prevention, and the natural course of the disease. This observation provides preliminary clinical context for prospective evaluation of FcRn inhibition but is insufficient to establish efficacy.