Author Affiliations: Department of Neurology, St Josef-Hospital, Ruhr University Bochum, Bochum (Drs Kleiter and Hellwig); Department of Neurology, Klinikum rechts der Isar, Technische Universität München (Dr Berthele); Institute for Clinical Neuroimmunology, Ludwig-Maximilians-University (Dr Kümpfel), Munich; Department of Neurology, Friedrich-Alexander University Erlangen, Erlangen (Dr Linker); Multiple Sclerosis Center, Department of Neurology, Heinrich-Heine-University Düsseldorf, Düsseldorf (Drs Hartung and Aktas); and NeuroCure Clinical Research and Clinical and Experimental Multiple Sclerosis Research Center, Charité University Medicine, Berlin (Dr Paul), Germany.
We appreciate Drs Govindarajan and Salgado describing a NMO IgG antibody–positive patient who had a 6-year course of clinical stability under natalizumab before becoming progressive. While such a long period with a good treatment response to natalizumab is noteworthy, several aspects of this patient are untypical for neuromyelitis optica (NMO). Only 13.7% of patients are older than 60 years at disease onset,1 8% have an elevated IgG index, and 16.4% show oligoclonal bands.2 Disease progression without relapses is uncommon in NMO,3 and it remains unclear whether optic neuritis was present, completing the full picture of NMO. In a patient with untypical clinical presentation, the verification of aquaporin 4 antibodies is of particular importance to make the diagnosis of NMO. Diagnostic tests applied to measure aquaporin 4 antibodies vary considerably regarding sensitivity and specificity, and immunohistochemical methods to detect NMO IgG additionally depend on the experience of the examiner.4
Kleiter I, Hellwig K, Berthele A, Kümpfel T, Linker RA, Hartung H, Paul F, Aktas O, Neuromyelitis Optica Study Group (NEMOS) FT. Is It Too Early to Predict the Failure of Natalizumab in NMO?—Reply. Arch Neurol. 2012;69(8):1085-1086. doi:10.1001/archneurol.2012.1316