Eosinophil Recruitment and Activity in CNS Lesions of MOG Antibody–Associated Myelitis Following Influenza Vaccination: A Case Report

The appearance of eosinophils in the cerebrospinal fluid (CSF) is considered atypical in patients with myelin oligodendrocyte glycoprotein (MOG) antibody–associated disease (MOGAD). In this article, we report the case of a 24‐year‐old male who received an influenza vaccine and subsequently presented with sensory disturbances in his limbs and trunk, accompanied by urinary retention. On spinal cord magnetic resonance imaging (MRI), T2‐weighted images showed intramedullary high‐intensity lesions. Meanwhile, brain MRI revealed no lesions. CSF testing showed pleocytosis (180 cells/μL), and eosinophils were present in approximately 6% of the CSF white blood cells. Additionally, MOG antibodies (MOG‐IgG) were present in the serum and CSF, leading to the diagnosis of MOG‐IgG–associated myelitis induced by immunization following influenza vaccination. It is speculated that perivascular infiltration of eosinophils can occur within demyelinating lesions in patients with MOGAD, possibly due to elevated levels of eosinophil‐associated cytokines and chemokines in the central nervous system (CNS) lesions. However, it remains unclear whether immunological responses triggered by vaccination contribute to the secretion of these mediators in such lesions.