Detection of Anti-Aquaporin-4 Antibodies in a Patient With Glioma: A Case Report

Anti-aquaporin-4 antibodies (AQP4-Ab) are highly specific for neuromyelitis optica spectrum disorder (NMOSD), but their prevalence in patients with non-inflammatory diseases, including malignant tumors, is unclear. A 54-year-old man presented with progressive weakness and dysesthesia of the right upper limb over 2 months. Cervical magnetic resonance imaging (MRI) revealed T2 hyperintense lesions in the area postrema and lower cervical/upper thoracic spinal cord, the latter of which demonstrated ring enhancement. Serum AQP4-Ab was positive on cell-based assay. He was initially diagnosed with NMOSD and treated with immunotherapy, but his neurological deficits progressed, and follow-up MRI demonstrated lesion expansion. Given the atypical course, a spinal cord biopsy was performed, and he was diagnosed with glioma with H3K27 M mutation; tumor cells were also AQP4-positive. Subsequent cancer-directed treatment led to improvement of spinal cord swelling and lesion enhancement. This case demonstrates that gliomas can present with both AQP4-Ab positivity and imaging features mimicking NMOSD, highlighting that the diagnosis of NMOSD should be based on comprehensive evaluation of antibody results, imaging findings, and the clinical course.