Glutamic acid decarboxylase autoimmunity with brainstem, extrapyramidal, and spinal cord dysfunction.

Area of Science:

• Neurology
• Immunology
• Neuroimmunology

Background:

• Glutamic acid decarboxylase (GAD65) autoimmunity is a rare condition.
• Neurological manifestations are often misdiagnosed as neurodegenerative or inflammatory disorders.
• GAD65 antibodies are implicated in autoimmune neurological diseases.

Purpose of the Study:

• To identify and describe novel neurological manifestations associated with GAD65 autoimmunity.
• To characterize the clinical features and demographic profiles of patients with GAD65 autoimmunity.
• To evaluate the diagnostic utility of GAD65 antibodies in neurological disorders.

Main Methods:

• Retrospective study of 62 patients with serum autoantibodies against GAD65.
• Indirect immunofluorescence and radioimmunoprecipitation assays used for antibody detection and characterization.
• Analysis of neurological symptoms, patient demographics, and co-existing autoimmune conditions.

Main Results:

• GAD65 autoimmunity presented with multifocal neurological symptoms including cerebellar ataxia, brainstem involvement, seizures, stiff-man phenomena, extrapyramidal signs, and myelopathy.
• Patients were predominantly women, with a median age of 50 years.
• African American patients were disproportionately affected, with a higher incidence of brainstem involvement.
• High GAD65 antibody levels (median, 1429 nmol/L) correlated with immunofluorescence titers.
• Co-existing autoimmune conditions such as type 1 diabetes mellitus, thyroid autoantibodies, and vitiligo were common.
• Some patients showed short-term benefit from immunosuppression.

Conclusions:

• The neurological spectrum of GAD65 autoimmunity is broad, encompassing brainstem, extrapyramidal, and spinal cord syndromes.
• GAD65 autoimmunity should be considered in patients with new-onset presumed neurodegenerative disorders and high GAD65 antibody levels (>20 nmol/L).
• Immunotherapy may be beneficial for patients with GAD65 autoimmunity, particularly those with high antibody titers.