There have been a series of case reports documenting the use of efgartigimod in Guillain–Barré syndrome (GBS), Neuromyelitis Optica Spectrum Disorder (NMOSD), anti-leucine-rich, glioma inactivated 1 (LGI1) antibody-associated autoimmune encephalitis (AE) and other disorders (8–11). The gene discussed is LGI1; the disease is neuromyelitis optica.