Anaplastic astrocytoma with aquaporin-4 positive in CSF: A case report

RATIONALE: An acute presentation with diffuse magnetic resonance imaging lesions can have a broad differential. Demyelination and malignancy are important considerations. Therefore, sometimes it is hard to differentiate glioma from some demyelinating diseases solely on imaging because of the similar clinical presentation and imaging features. Detection of highly specific serum autoantibody marker aquaporin-4 (AQP4)-IgG positivity has helped to define a category of neuromyelitis optica spectrum disorders (NMOSD), but the test of AQP4 antibody has not been reported in patients with glioma. PATIENTS CONCERNS AND DIAGNOSES: We report a case of a 56-year-old woman with cerebrospinal fluid (CSF) positive aquaporin-4 antibodies with initial response to immune therapy and secondary deterioration. A surgical biopsy revealed an anaplastic astrocytoma. INTERVENTIONS AND OUTCOMES: After the admission the patient was treated with a short course of intravenous steroid agents. After anaplastic astrocytoma was diagnosed, she began to receive a radiation treatment and soon later experienced a clinical deterioration with frequent epilepsy seizure and disturbance of consciousness within a few months. LESSON: This case indicates that tumors could lead to polyclonal antibody responses as in this case with aquaporin-4 and myelin oligodendrocyte glycoprotein antibodies. The absence of a typical clinical phenotype and lack of sustained response to immunotherapy should alert the clinical suspicion of an alternative diagnosis. When AQP4 antibody was detected positive in CSF of a patient but negative in serum, differential diagnosis should especially be considered.