Paraneoplastic Neuromyelitis Optica Spectrum Disorder: A Rare Case of Advanced Breast Cancer with Intractable Nausea and Vomiting.

BACKGROUND Neuromyelitis optica spectrum disorder (NMOSD) is a demyelinating disease of the central nervous system that includes the triad of transverse myelitis, optic neuritis, and area postrema syndrome (APS), characterized by intractable nausea and vomiting. NMOSD can be part of a paraneoplastic syndrome and is associated with seropositivity to aquaporin-4 (AQP-4). We present a patient with uncontrollable nausea and vomiting who developed herpes zoster and acute myelitis and was finally diagnosed with paraneoplastic NMOSD due to breast cancer. CASE REPORT A 51-year-old woman was hospitalized due to 2 weeks of intractable nausea and vomiting. Although contrast-enhanced thoracoabdominal computed tomography (CT) on day 4 suggested breast cancer in her left breast, the etiology of her symptoms remained unknown. On day 13, she developed herpes zoster, followed by acute myelitis on day 25. Magnetic resonance imaging (MRI) showing longitudinal extensive transverse myelitis and an elevated serum AQP-4 antibody level led to the diagnosis of NMOSD. Brain MRI detected a small lesion in the dorsal medulla oblongata, which explained the preceding APS. After starting intravenous methylprednisolone pulse therapy, her nausea and vomiting rapidly subsided. Breast cancer was resected on day 63, and immunohistochemical staining revealed overexpression of AQP-4 in the tumor cells, suggesting paraneoplastic NMOSD. CONCLUSIONS This report has highlighted the presentation and diagnosis of NMOSD and supports the possibility that this can present as part of a paraneoplastic syndrome. In addition, diagnosis of NMOSD preceded by APS requires meticulous history taking and careful interpretation of MRI in the dorsal medulla oblongata.