A case report on αIN antibody-mediated paraneoplastic cerebellar ataxia.

BACKGROUND

α-internexin (αIN) antibody-associated paraneoplastic cerebellar ataxia is a rare neurological disorder, with limited cases reported worldwide. This study aims to present a detailed clinical course and diagnostic approach for this condition.

CASE PRESENTATION: A 68-year-old female presented with subacute blurred vision, lower limb weakness, and dysarthria following a SARS-CoV-2 infection. Neurological examination revealed nystagmus, dysarthria, and limb ataxia. Arterial spin-labeling MRI showed hypoperfusion in bilateral cerebellar hemispheres. Serum and cerebrospinal fluid (CSF) were positive for αIN antibodies. Bronchoscopy suggested small-cell lung cancer. The patient received intravenous immunoglobulin therapy with partial symptom improvement.

CONCLUSION

αIN antibodies represent a novel and important biomarker for paraneoplastic neurological syndromes. Early detection and immunotherapy may improve outcomes, particularly when associated with underlying malignancies. This case adds to the limited literature on neuronal intermediate filament autoimmunity.