A case series of five patients with anti-γ-aminobutyric acid type B receptor encephalitis

Objective To investigate the clinical features, treatment and prognosis of anti-γ-aminobutyric acid type B receptor (GABAB R) encephalitis. Methods Retrospective analysis of five patients of anti-GABABR encephalitis from the Department of Neurology, the University of Hong Kong-Shenzhen Hospital from September 2017 to June 2019 was carried out. Clinical manifestations, auxiliary examination, and treatment were analyzed. The patients were followed up for 3.5-23.0 months to assess their prognosis. Results Five cases of anti-GABABR encephalitis (19-81 years old) presented acute onset, with refractory epilepsy as the main clinical manifestation. There were hyperintensive signals on T2/fluid attenuated inversion recovery in four patients′ temporal lobe and hippocampus. Electroencephalogram showed slow wave or epileptic discharge; Lung mass was found in four patients, and all were small cell lung cancer. Five cases had poor response to first-line immunotherapy (intravenous use of pulse methylprednisolone, high dose immunoglobulin or plasma exchange), then three patients received second-line immunotherapy (rituximab, cyclophosphamide), two of whom with tumor also received tumor chemotherapy. Patients who received second-line treatment and tumor chemotherapy showed better outcome than those who only received first-line treatment. Conclusions Anti-GABABR encephalitis present with limbic encephalitis syndromes characterized by refractory epilepsy. For patients with poor response to first-line immunotherapy, initiating second-line immunotherapy as soon as possible can improve the prognosis significantly. Key words: Receptors, GABA-B; Autoimmune diseases; Limbic encephalitis; Immunosuppression