Glutamic acid decarboxylase (GAD)-65 antibodies-associated autoimmune neurological syndrome

Glutamic acid decarboxylase 65 antibody–associated neurological syndrome (GAD65-AINS) is an autoimmune disorder mediated by anti-GAD65 antibodies, with clinical phenotypes including stiff-person spectrum disorders(SPS), limbic encephalitis, cerebellar ataxia, and drug-resistant epilepsy. As the rate-limiting enzyme in GABA synthesis, GAD65 exhibits conformational plasticity, which forms the molecular basis for autoimmune targeting. Genetic susceptibility involves HLA regions (DR3, DR4) and non-HLA immune regulatory genes (e.g., PTPN22, CTLA4), demonstrating a polygenic characteristic. Pathogenic mechanisms involve T-cell-mediated cellular immunity, direct functional interference by antibodies, complement-dependent humoral immune effects, and synergistic enhancement of pathological effects by coexisting antibodies (e.g., anti-CN1A). Diagnosis requires integration of clinical phenotypes, quantitative antibody testing (serum ELISA ≥10,000 IU/mL or RIA ≥20 nmol/L), intrathecal synthesis evidence in CSF, and imaging evaluation. High-titer antibodies are the core diagnostic basis for SPS, but must be interpreted in conjunction with clinical findings.Treatment follows a stratified principle: symptomatic management is based on GABAergic enhancers, while immunotherapy includes IVIg, glucocorticoids, and rituximab, etc. Treatment responses vary significantly across phenotypes, with better responses observed in SPS and limbic encephalitis, followed by cerebellar ataxia, and limited responses in GAD65-related epilepsy, often requiring adjunctive antiepileptic drugs. Most patients require long-term immunomodulatory therapy. Future research should elucidate the synergistic mechanisms between T cells and antibodies, develop biomarkers, explore novel targeted therapies such as FcRn antagonists, and promote the transformation of precision medicine models.