Efgartigimod treatment for therapy-refractory autoimmune encephalitis with coexistent NMDAR and LGI1 antibodies: a case report and literature review.

The Fc receptor (FcRn) inhibitors can ameliorate autoimmune conditions such as myasthenia gravis through a rapid and specific clearance of serum IgG levels, and they also have potential for future use in a wider variety of antibody-mediated autoimmune diseases. Some patients with therapy-refractory autoimmune encephalitis (AE) continue to be unresponsive to initial and secondary treatment regimens. A 32-year-old male presented with predominant psychiatric symptoms and seizures, along with imaging evidence indicating multifocal cerebral cortical involvement. Neural antibody testing revealed dual positivity for N-methyl-D-aspartate receptor (NMDAR) and leucine-rich glioma-inactivated 1 (LGI1) antibodies in both serum and cerebrospinal fluid (CSF). Human leukocyte antigen (HLA) genotyping revealed the presence of the DQB1*03:01 and DQB1*06:01 alleles in the patient. Treatment with efgartigimod, the FcRn inhibitor, led to significant clinical improvements accompanied by a significant decrease in both anti-NMDAR and anti-LGI1 antibody levels. Herein, we report a rare case of therapy-refractory anti-NMDAR AE coexisting with positive LGI1 antibodies. Efgartigimod demonstrates promising potential for treating antibody-mediated AE. Clinical trial number Not applicable.