The main IgG4 antibodies in autoimmune neurology are (a) MuSK IgG in myasthenia, (b) nodal/paranodal Neurofascin-155 and CASPR1 IgG in CIDP, (c) LGI1- and CASPR2-IgG in autoimmune encephalitis with IgG 1:4 ratio reported to correlate with clinical outcomes, and (d) anti-IgLON5 associated with a possibly autoimmune neurodegenerative process, presenting with bulbar syndromes, sleep apnea, and REM-sleep behavior disorder. The gene discussed is LGI1; the disease is autoimmune encephalitis.