Jac Williams, Sarah McGlasson, Sarosh Irani, Darragh Duffy, Yanick Crow, David Hunt, Katy Murray, Robert Wilson, Andrew P Jackson, Alexa Jury, Mathieu Rodero, Vincent Bondet, Anu Jacob, Shahd Hamid, Nuno Cordeiro, Ondrej Dolezal, Patrick Statham, Stewart Wiseman, Joanna Wardlaw, Christina Hertel, Adrian Hayday, Anne Rowling Clinic [Edinburgh, UK], University of Edinburgh, Medical Research Council Institute of Genetics and Molecular Medicine [Edinburgh, UK], Oxford Autoimmune Neurology Group [Oxford, UK], University of Oxford, Immunobiologie des Cellules dendritiques, Institut Pasteur [Paris] (IP)-Institut National de la Santé et de la Recherche Médicale (INSERM), DH is supported by the Wellcome Trust (215621/Z/19/Z) and the Medical Research Foundation. YC is supported by an European Research Council advanced grant (786142-E-T1IFNs). YC and DH are supported by Connect Immune research (Multiple Sclerosis Society, Juvenile Diabetes Research Foundation, Versus Arthritis). AJ is supported by the UK Medical Research Council. SRI is supported by the Wellcome Trust (104079/Z/14/Z), the British Medical Association's Vera Down (2013) and Margaret Temple (2017) grants, and Epilepsy Research UK (P1201). The research was funded by the National Institute for Health Research (NIHR) Oxford Biomedical Research Centre., We thank the Uppsala Monitoring Centre (Uppsala, Sweden) and the UK Medicines and Healthcare products Regulatory Agency for providing spontaneous reporting data. We thank our patients for willingness and consent to report these cases. Patients 1, 3, and 4 were enrolled in clinical studies approved by: Leeds (East) Research Ethics Committee (10/H1307/132, patient 3) and South-East Scotland Research Ethics Committee 01 (14/SS/0003, patients 1 and 4). The Scottish Neuromyelitis Optica Spectrum Disorder Clinic is part of the NHS NMO UK specialised service., Scottish NMOSD study group : Murray K, Wilson R, Jackson AP, Jury A, Rodero M, Bondet V, Jacob A, Hamid S, Cordeiro N, Dolezal O, Statham P, Wiseman S, Wardlaw J, Hertel C, Hayday A., Laboratoire de Chimie et de Biochimie Pharmacologiques et Toxicologiques (LCBPT - UMR 8601), Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), University of Oxford [Oxford], Immunologie Translationnelle - Translational Immunology, Institut Pasteur [Paris], Imagine - Institut des maladies génétiques (IHU) (Imagine - U1163), Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Dept Neurology, Western General Hospital, Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut Pasteur [Paris], Imagine - Institut des maladies génétiques (IMAGINE - U1163), and Vougny, Marie-Christine