Anti-metabotropic glutamate receptor 1 antibodies associated encephalitis: a case report / 中华神经科杂志

ABSTRACT

Objective:To establish a tissue based assay and in-house cell based assay combined system to screen anti-metabotropic glutamate receptor 1 antibodies in a case of previously idiopathic encephalitis with prominent cerebellar ataxia and make the final diagnosis, and to summarize and analyze clinical characteristics and treatment response of the disease.Methods:A middle-aged woman admitted to Department of Neurology, People's Liberation Army General Hospical Accredited to the Sixth Medical Center in January 9, 2020, who presented with acute dizziness, unsteady gait and developed head titubation, repeated language and calculation impairment was reported. The patient′s serum and cerebrospinal fluid were firstly tested with commercial kits for conventional neural antibodies.Then samples were incubated with rat hippocampus, cerebellum and human embryonic kidney 293 cells transfected with metabotropic glutamate receptor 1 plasmid to screen extra antibodies by indirect immunofluorescence method. By reviewing literature, physical functions of metabotropic glutamate receptor 1 and clinical features of anti-metabotropic glutamate receptor 1 antibodies associated encephalitis were summarized.Results:The patient was neural antibodies negative with commercial kits. Further investigation showed neuropil staining pattern after her serum and cerebral spinal fluid were incubated with rat brain slices. The characteristic "Medusa head" staining pattern of Purkinje cells in cerebellum was also noticed. Along with her previous head titubation symptom, an in-house cell based assay using human embryonic kidney 293 cells transfected with metabotropic glutamate receptor 1 plasmid was developed and proved the existence of anti-metabotropic glutamate receptor 1 antibodies. The final diagnosis of anti-metabotropic glutamate receptor 1 antibodies associated encephalitis was made. One-year follow-up revealed her serum antibodies titers dramatically decreased and cerebrospinal fluid antibodies were negative after using steroids and intravenous immunoglobulin, but still left prominent cerebellum atrophy and severe ataxia.Conclusions:Anti-metabotropic glutamate receptor 1 antibodies may cause acute encephalitis. Cerebellar ataxia and head titubation are characteristic symptoms of metabotropic glutamate receptor 1 autoimmunity. The response to immunotherapies is limited and patients may have severe neurological deficits.