From the MRC Centre for Neuromuscular Disease, Neuroimmunology and CSF Laboratory (S.K., O.J.Z., H.M., A.C., M.M.R., M.P.L.), Institute of Neurology, Cancer Division (D.F., J.B., A.C., K.Y., S.D.), Department of Endocrinology (F.C., S.E.B., M.P.L.), and Division of Neuropathology, National Hospital for Neurology and Neurosurgery (Z.J., S.B.), University College London NHS Foundation Trust (S.K.), National Hospital for Neurology and Neurosurgery; Department of Neuromuscular Diseases (S.K., O.J.Z., H.M., A.C., M.M.R., M.P.L.), UCL Queen Square Institute of Neurology; and Department of Clinical Neurosciences (J.F., S.R.), John Radcliffe Hospital, Oxford, UK.