Glutamate Receptor Antibodies in Autoimmune Central Nervous System Disease: Basic Mechanisms, Clinical Features, and Antibody Detection

Anti-metabolic glutamate receptor 5 encephalitis with gangliocytoma: a case and review of the literature

BACKGROUND

There are very limited reports on anti-metabolic glutamate receptor5 (mGluR5) encephalitis, especially lacking of pediatric research. The disease was mostly accompanied by tumors, mainly Hodgkin's lymphoma. No reports of other tumors, such as gangliocytoma have been reported to associate with anti-mGluR5 encephalitis so far.

CASE PRESENTATION AND LITERATURE REVIEWS

We reported a case of a 12-year-old boy with anti-mGluR5 encephalitis complicated with gangliocytoma. The patient suffered from mental disorders including auditory hallucination, and sleep disorders. His cranial magnetic resonance imaging (MRI) showed an abnormality in the right insular lobe. Autoimmune encephalitis antibodies testing was positive for mGluR5 IgG antibody both in cerebrospinal fluid and serum (1:3.2, 1:100 respectively). Abdominal CT indicated a mass in left retroperitoneal confirmed with gangliocytoma via pathology. The patient underwent resection of gangliocytoma. After first-line immunotherapy (glucocorticoid, gamma globulin), his condition was improved. Furthermore, we provide a summary of 6 pediatric cases of Anti-mGluR5 encephalitis. Most of them complicated with Hodgkin's lymphoma, except the case currently reported comorbid with gangliocytoma. The curative effect is satisfactory.

CONCLUSIONS

We report the first patient with anti-mGlur5 encephalitis complicated with gangliocytoma. It suggests that in addition to paying attention to the common lymphoma associated with anti-mGlur5 encephalitis, we should also screen the possibility of other tumors for early detection of the cause, active treatment and prevention of recurrence.

Case Report: Autoimmune encephalitis and other neurological syndromes with rare neuronal surface antibody in children after hematopoietic stem cell transplantation

Introduction

Neuronal surface antibody syndromes (NSAS) encompass a growing set of autoimmune neurological disorders, with their predominant clinical presentation being autoimmune encephalitis (AE). The most extensively documented form within NSAS is anti-N-methyl-D-aspartate receptor (NMDAR) autoimmunity. In contrast, other NSAS, such as anti-metabotropic glutamate receptor-5 (mGluR5) autoimmunity, are less common and less comprehensively characterized, particularly in pediatric cases.

Case description

In this instance, we present the case of a 7-year-old girl who exhibited abnormal behaviors following hematopoietic stem cell transplantation (HSCT). She received a diagnosis of anti-mGluR5 AE, and her Electroencephalogram (EEG) displayed an increased number of generalized slow waves during wakefulness. Treatment involved intravenous administration of gamma globulin and methylprednisolone, followed by oral prednisone tablets. Levetiracetam was introduced as an antiepileptic therapy during the pulse steroid therapy. Notably, the abnormal behaviors exhibited significant improvement after treatment.

Conclusions

To the best of our knowledge, this is the first report of rare pediatric NSAS involving anti-mGluR5 AE following HSCT. Enhancing our understanding and characterization of this condition may facilitate its recognition and treatment in children. Serum antibody testing could enable early identification and treatment of anti-mGluR5 AE.

Anti-mGluR1 encephalitis: Case illustration and systematic review

Background

The literature for immune-mediated neurological disorders is evolving like no other field of neurological illnesses. Many new antibodies or disorders have been described in the last decade. The cerebellum is a brain structure susceptible to these immune-mediated pathologies, and anti-metabotropic glutamate receptor 1 (mGluR1) antibody has a predilection to the cerebellar tissue. Anti-mGluR1 encephalitis is a rare autoimmune disease affecting the central and peripheral nervous systems, triggering an acute or subacute cerebellar syndrome with varying degrees of severity. Anti-mGluR1 encephalitis is a rare autoimmune disease affecting the central nervous system. We aimed to systematically review reported cases of anti-mGluR1 encephalitis and summarize their clinical presentation, management, outcomes, and case reports.

Methods

A search of the PubMed and Google Scholar databases was conducted and included all cases of anti-mGluR1 encephalitis published in English before October 1, 2022. A comprehensive systematic review was conducted using "metabotropic glutamate receptor type 1," "mGluR1," autoantibodies," "autoantibodies," "autoimmunity," and "antibody" as keywords. The risk of bias assessment of the evidence was performed using appropriate tools. The qualitative variables were presented as frequency and percentage.

Results

Including our case, 36 cases of anti-mGluR1 encephalitis (19 males, median age 52.5 years, 11.1% pediatric cases) have been reported. The most common clinical manifestations are ataxia, dysarthria, and nystagmus. Initial imaging was normal in 44.4% of patients; however, 75% of patients showed abnormality later in the disease course. The first-line therapy options include glucocorticoids, intravenous immunoglobulin, and plasma exchange. Rituximab is the most commonly used second-line treatment. Complete remission was achieved in only 22.2% of patients, and 61.8% were disabled by the end of their course.

Conclusion

Anti-mGluR1 encephalitis manifests as symptoms of cerebellar pathology. Although the natural history has not been completely elucidated, early diagnosis with prompt initiation of immunotherapy could be imperative. Any patient suspected to have autoimmune cerebellitis should be tested for the presence of anti-mGluR1 antibody in the serum and cerebrospinal fluid. Escalation to an aggressive therapy approach should be applied in cases that do not respond to first-line therapies, and extended follow-up durations are required in all cases.