FBDS were exclusive to patients with LGI1 antibodies (P < 0.0001) who had more seizures (P = 0.01) than patients with CASPR2 antibodies, where peripheral nerve features of neuromyotonia (P = 0.0003) and neuropathic pain (P < 0.0001) were preferentially associated. The gene discussed is CNTNAP2; the disease is Isaacs syndrome.