Cerebellar ataxia and myeloradiculopathy associated with AP3B2 antibody: a case report and literature review

• Published in: Journal of neurology 2021-11, Vol.268 (11), p.4163-4169
• Main Authors: Mange, Liu, Haitao, Ren, Lixin, Zhou, Siyuan, Fan, Jing, Wang, Hongzhi, Guan
• Format: Article
• Language: English
• Subjects: Antibodies; Ataxia; Autoantibodies; Case reports; Central nervous system; Cerebellar ataxia; Cerebellum; Cerebrospinal fluid; Coat protein; Cytoplasm; Dorsal root ganglia; Gait; Immunoglobulin G; Immunotherapy; Intravenous administration; Literature reviews; Malignancy; Medicine; Medicine & Public Health; Movement disorders; Mycophenolate mofetil; Mycophenolic acid; Neurology; Neuroradiology; Neurosciences; Original Communication; Paresthesia; Patients; Prednisone; Purkinje cells; Somatosensory cortex; Spinal cord; Substantia grisea; Synapses
• ISSN: 0340-5354; 1432-1459
• DOI: 10.1007/s00415-021-10496-8

Background AP3B2 is one of the subunits of vesicle coat protein AP3 and is specifically expressed in central nervous system neurons. AP3B2 antibody has been reported in patients with autoimmune cerebellar ataxia and various extracerebellar symptoms. However, there have been few reports on its clinical features and treatment response. Methods We report a 47-year-old man with AP3B2 antibody who presented with insidious-onset paresthesia and gait disturbance. His serum and cerebrospinal fluid (CSF) showed reactivity with the cytoplasm of Purkinje cells and granular layer synapses comparable to the reported specific pattern of anti-AP3B2 IgG, and this was confirmed by a cell-based assay. His symptoms improved after the administration of intravenous immunoglobulin, and oral prednisone and mycophenolate mofetil. Extensive examination and long-term follow-up showed no evidence of malignancy. A literature review was included to emphasize the neurological syndrome associated with this rare autoantibody. Results Eleven cases with AP3B2 antibody, including our patient, were identified. The diversity of symptoms, including cerebellar and sensory ataxia, paresthesia, and weakness, was in line with the extensive binding of AP3B2 antibody to the spinal cord gray matter, dorsal root ganglia, cerebellar cortex, and nucleus. In the CSF, half of patients had elevated white blood cell counts, increased protein concentrations, or CSF-specific oligoclonal bands. All previous cases had subacute onsets and no improvement was noted after immunotherapy. Conclusion Our case indicated that disorders associated with AP3B2 antibody can also start insidiously. Immunotherapy is warranted given the possibility of clinical improvement.