LGI1 and Isaacs syndrome: Almost all of the antibodies from patients with LE, FBDS or MoS, and some with NMT, are directed against the extracellular domains of LGI1 or CASPR2, and the antibodies often co-immunoprecipitate the 125I-αDTX-labelled Kv1 subunits from brain extracts.7–10 Patients with LGI1 or CASPR2 antibodies often respond very well to immunotherapies, and their antibody levels broadly correlate with clinical status.7, 11, 12