[Clinical features of five Japanese cases with leucine-rich glioma inactivated-1 (LGI1) antibody-positive encephalitis].

We studied the clinical features of five Japanese cases with leucine-rich glioma inactivated-1 (LGI1) antibody-positive encephalitis. Their symptoms included seizures, hallucinations, memory impairment, apathy, anxiety, agitation, faciobrachial dystonic seizure (FBDS), and ictal piloerection. All five patients showed hippocampal fluid attenuated inversion recovery (FLAIR) hyperintensity on brain MRI even though their cell counts of cerebrospinal fluid (CSF) were normal range. Four patients had syndrome of inappropriate secretion of antidiuretic hormone. One patient with FBDS also showed basal ganglia lesion on her brain MRI. Sodium channel blockers apparently lowered the frequency of FBDS. One patient had a thyroid cancer and underwent thyroidectomy. Substantial response to immunotherapy was seen in four out of five cases. At follow-up ≥2 years, all five patients had never relapsed. In cases of limbic encephalitis with normal CSF cell counts and hyponatremia, we should consider LGI1 antibody-positive encephalitis and conduct immunotherapy immediately.