Case Report: Anti-LGI1 encephalitis during FcRn inhibition with efgartigimod for myasthenia gravis: implications for the limitations of IgG recycling blockade - PubMed
5 hours ago
- #Myasthenia gravis
- #FcRn inhibition
- #Anti-LGI1 encephalitis
- A 72-year-old woman with thymoma-associated myasthenia gravis (MG) developed anti-LGI1 antibody-associated autoimmune encephalitis while receiving efgartigimod, an FcRn antagonist that reduces IgG levels.
- Despite treatment with efgartigimod and reduced serum IgG, the patient presented with rapid memory impairment; MRI showed bilateral medial temporal lobe hyperintensities, and serology confirmed anti-LGI1 antibodies.
- Cerebrospinal fluid analysis was negative for LGI1 antibodies and showed a normal IgG index, indicating no intrathecal IgG synthesis, suggesting pathogenic antibodies originated peripherally.
- High-dose intravenous methylprednisolone therapy led to significant clinical improvement, highlighting the treatable nature of the encephalitis.
- This case demonstrates that FcRn inhibition may not fully prevent central nervous system autoimmunity, particularly in thymoma-associated immune dysregulation, underscoring its pharmacodynamic limitations.