Efgartigimod for steroid-resistant autoimmune glial fibrillary acidic protein astrocytopathy: a case report and literature review

BACKGROUND: Neonatal Fc receptor (FcRn) inhibitors rapidly and specifically clear serum immunoglobulin G (IgG) levels and, therefore, are increasingly used for the treatment of neurological autoimmune diseases, such as myasthenia gravis. However, whether FcRn inhibitors could alleviate steroid-unresponsive glial fibrillary acidic protein astrocytopathy (GFAP-A) has not been reported. CASE PRESENTATION: We report a case of a 68-year-old male patient who presented with gait instability and numbness in the left hand. Cranial magnetic resonance imaging (MRI) revealed multiple demyelinating lesions. The initial clinical diagnosis was demyelinating encephalopathy. After 1 month of intravenous methylprednisolone pulse therapy, followed by sequential oral prednisone, the patient's gait instability did not improve. Upon re-examination at our hospital, cranial MRI revealed no significant changes in the lesions. Testing for central nervous system demyelinating antibodies revealed serum anti-GFAP IgG antibody (titer 1:100), cerebrospinal fluid anti-GFAP IgG antibody (titer 1:1), and negative result for oligoclonal bands in blood and the cerebrospinal fluid. The final diagnosis was GFAP-A. Treatment with the FcRn inhibitor efgartigimod significantly improved clinical symptoms and brain lesions. CONCLUSIONS: This rare case indicates that efgartigimod is a promising treatment option for steroid-unresponsive GFAP-A.