GAD antibody-spectrum disorders: case report

Objectives: Report the clinical case of GAD antibody-spectrum disorders (antiGAD-SD) during therapy with intravenous immunoglobulins. AntiGAD-SD has various phenotypic manifestations, however there is little published data on the features of the clinical course. There is also little data of therapy efficacy. Methods: Description of a clinical case of antiGAD-SD beginning at 10 y.o. Results: Female, 10 y.o., disease started in May 2019, after sinusitis. Symptoms include: progressive vertigo, drowsiness, weakness of the eyelids, tetraparesis (patient unable walk independently), and urinary incontinence. Four relapses occurred over the course of six months, with varying degrees of severity. Brain and cervical MRI: normal. Lumbar puncture: normal. Oligoclonal bands: negative. AntiNMDR, antiLGI-S, and antiCASPR-S: all negative. AntiGAD: 49.5 IU/ml (high level). In December 2020, intravenous immunoglobulins were started (0.8 g/kg every 4-6 weeks) with clinical stabilization. After two months therapy discontinuation relapse occurred, manifesting in gait ataxia and muscle weakness. Since August 2021, IVIG therapy has been resumed (1 g/kg every 4-6 weeks). During this time, two mild exacerbations (vertigo and gait ataxia up to 5 days) after upper respiratory tract infections were noted. The patient continues to receive therapy. Conclusion: In cases with episodes of vertigo, ataxia, muscle weakness and normal MRI, antiGAD-SD must be excluded. IVIG therapy may be the best option for children to reduce the frequency and severity of relapses.
Keywords: autoimmun encephalopathy; GAD antibody-spectrum disorders; cerebellar ataxia;