Aquaporin-4 Antibody-Positive Neuromyelitis Optica Spectrum Disorder developed in a Patient with Breast Cancer

초록

Background: Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory demyelinating disease of the central nervous system. NMOSD could be associated with other autoimmune diseases. In addition, some reports suggest that NMOSD could be one of the paraneoplastic syndromes, especially when it occurs in a relatively old age. Objective: Herein, we report aquaporin-4 antibody-positive NMOSD that occurred in a patient with breast cancer. Methods: A 68-year-old woman, who did not have any previous autoimmune disorders, came to the emergency room with a drowsy mentality and weakness in both lower extremities. She was diagnosed with right breast cancer (stage 1) 10 months ago and undergoing radiation therapy and chemotherapy. She had a 10-days history of intractable vomiting and a 7-days history of a painful sensation in her right arm and flank. At the time of admission, she was drowsy (Glasgow coma scale score: 12) and could not walk independently. Neurologic examination revealed the motor weakness of lower extremities (MRC grade 2) and positive pathologic reflex. Laboratory tests showed hypoosmolar hyponatremia, hypokalemia, and leukocytosis. The cerebrospinal fluid (CSF) study revealed leukocytosis (14/μL) with normal protein level. The cytology test revealed no malignant cells in CSF. Brain MRI showed multifocal T2 high signal intensity (HSI) lesions without enhancement in multiple territories. In addition, spine MRI revealed T2 HSI lesions with enhancement at multiple levels. Further laboratory tests showed that the serum aquaporin-4 antibody, which was tested by cell-based assay, was positive (3+). Results: She was treated with steroid and antiviral agents since viral encephalitis was not excluded at the time of admission. After five days of treatment, her mental status improved. However, her weakness in both legs was not improved, so intravenous immunoglobulin (0.4g/kg/day) was administered for five consecutive days, and oral steroids were maintained. Her symptoms gradually improved, and she could walk with a walker after five months. Conclusion: Paraneoplastic neurologic involvement is a rare condition. However, physicians need to consider not just metastasis but NMOSD in patients with cancer who presents neurologic deficits.