Paraneoplastic neuromyelitis optica and ovarian teratoma: A case series

•Paraneoplastic forms of neuromyelitis optica (NMOSD) may occur in rare cases.•We describe 3 cases of NMOSD in the context of underlying ovarian teratoma.•All three patients presented initially with area postrema symptomatology.•Strong immune infiltrates colocalize with AQP4+ glial component in the teratomas. Neuromyelitis optica spectrum disorder (NMOSD) is a rare inflammatory disease of the central nervous system, characterized by the presence of auto-antibodies directed against aquaporin-4 (AQP4) expressed on astrocyte end-feet. Despite NMOSD does not primarily belong to the spectrum of paraneoplastic neurological syndromes, rare cases of association with neoplasia have been outlined. Here, we report the association of NMOSD with ovarian teratoma in 3 cases. Pathological analysis of teratomas revealed glial component strongly expressing AQP4 and closely localized to immune infiltrates. Our series highlight the rare association of teratoma with NMOSD and the possible paraneoplastic mechanism.