Novel, Rare, and Underdetected: Antineuronal Antibodies in Pediatric Autoimmune Movement Disorders

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Background/Purpose: Autoimmune disorders account 42% of all acute-onset movement disorders in children. We report on three patients with movement disorders and antineuronal antibodies, who show different clinical pictures compared to adults. Two infants were positive for Neurochondrin (NCDN) antibodies and showed self-limiting ataxia and limb dystonia. One 7-year-old boy showed progressive spastic ataxia anti-adenylate kinase5 (AK5) in serum and CSF was detected. Objective: Clarifying the pathogenic role of these rare antibodies. Methods: A bibliographic search on PubMed was performed (last checked on May 31, 2024). Results: NCDN is located in neurons of cerebellum, amygdala, and hippocampus. Cerebellar ataxia associated with anti-NCDN antibodies has been described in 19 cases. Antibodies cause symptoms of movement disorders such as cerebellar ataxia, dystonia, and encephalopathy with rapid clinical progression in children. Response to immunotherapy is poor and relapses are common. AK5 is a metabolic protein located in the cytosol of neuronal cells in the brain. The antibody typically causes limbic type encephalitis in male adults. Human leukocyte antigen (HLA) genetic predispositions were described to be associated. AK5 antibody is targeting the intracellular antigen and shows poor therapeutic response. Conclusion: We suppose that anti-NCDN caused cerebellar ataxia and dystonia in our first two patients with a self-limiting course. Anti-AK5 is unknown in children and has not been associated with movement disorders. Trio-Exom-analysis and follow-up antibody analysis as well as response to immunosuppressive therapy is pending and will be available at the time of the presentation. Our cases demonstrate the difficulties of interpreting novel antineuronal antibodies in pediatric patients, especially if symptoms are different to those of adults, but could widen the clinical profile and therapy chances in the future. Publication History Article published online: 08 October 2024 Georg Thieme Verlag KG Stuttgart · New York

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