To report the clinical and paraclinical features of a case series with anti-IgLON5 antibody related encephalopathy.

One hundred and fifty patients with sleep disorders and subacute or chronic onset of movement disorders, parkinsonism or bulbar palsy were included. The serum and cerebrospinal fluid specimens of these patients were screened for anti-IgLON5 antibody. The clinical and paraclinical features of patients with seropositive anti-IgLON5 antibody were summarized.

Three patients with seropositive anti-IgLON5 antibody were identified, with one female and two males. The onset age ranged from 61 to 64 years. Case 1 presented with symptoms of involuntary movement, unsteady walk and insomnia; case 2 with symptoms of insomnia, sleep behavioral disorder, psychiatric behavior and dysphagia; case 3 with symptoms of insomnia, sleep behavioral disorder, dysarthria, and tremor. When examined by polysomnography, obstructive sleep apnea syndrome was revealed in cases 1 and 2, serious insomnia was found in cases 2 and 3, and sleep behavioral disorder was revealed in case 2. All three patients were positive for HLA-DQB1^*0501, and cases 2 and 3 were positive for HLA-DRB1^*1001. All three patients received immunotherapy and only one patient (case 1) responded well to immunotherapy with intravenous immunoglobulin, steroids and mycophenolate mofetil.

Anti-IgLON5-related encephalopathy is a rare disease with distinct clinical features of both autoimmune disorders and neurodegeneration disorders. These patients may benefit from immunotherapy.

Autoantibodies; Tauopathy; Brain diseases; Sleep disorders; Immunotherapy