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Anti-SEZ6L2 antibody-associated autoimmune encephalitis initially misdiagnosed as cerebral infarction: a case report and narrative literature review

Year: 2026

Type: article

Abstract: Background: Anti-SEZ6L2 antibody-associated autoimmune encephalitis is a rare immune-mediated neurological disorder frequently misdiagnosed as cerebrovascular or neurodegenerative diseases due to clinical overlap with stroke and limited disease awareness. Case presentation: We report a 53-year-old female presenting with acute stroke-like symptoms and patent foramen ovale (PFO), initially misdiagnosed with acute cerebral infarction. The patient developed progressive dysarthria, cerebellar ataxia, cognitive decline, seizures, and psychiatric disturbances. Antiplatelet therapy and PFO closure provided no clinical benefit. Comprehensive workup revealed mildly elevated CSF protein, positive anti-SEZ6L2 antibodies in serum (1:1000) and CSF (1:100), brainstem/somatosensory pathway damage on neurophysiology, and only Fazekas grade 1 white matter hyperintensities on MRI. Immune markers suggested systemic immune dysfunction linked to prior cervical cancer and chemoradiotherapy. The patient stabilized after combined immunotherapy with double filtration plasmapheresis, rituximab, mycophenolate mofetil, and levetiracetam. A systematic literature review with pooled analysis of 24 previously published global cases demonstrated: 70.83% middle-aged/elderly females; core symptoms of cerebellar ataxia (95.83%) and dysarthria (75%); 66.67% with cerebellar atrophy on imaging; 12.50% with paraneoplastic syndrome; and only 58.33% achieving mild symptom improvement after immunotherapy. Conclusions: This case highlights the necessity of early autoimmune antibody screening for unexplained progressive cerebellar ataxia, particularly in patients presenting with stroke-mimic episodes. Early individualized combination immunotherapy and long-term tumor surveillance are essential for improved prognosis. Further large-scale studies are needed to elucidate pathogenesis and standardize treatment protocols for this rare condition.

Source: BMC Neurology

DOI: 10.1186/s12883-026-05507-y