Background and objectives Neuromyelitis optica spectrum disorders (NMOSDs) are a group of diseases mainly characterised by recurrent optic neuritis and/or myelitis. Most cases are associated with a pathogenic antibody against aquaporin-4 (AQP4-Ab), while some patients display autoantibodies targeting the myelin oligodendrocyte glycoprotein (myelin oligodendrocyte glycoprotein antibodies (MOG-Abs)). Anti-Argonaute antibodies (Ago-Abs) were first described in patients with rheumatological conditions and were recently reported as a potential biomarker in patients with neurological disorders. The aims of the study were to investigate if Ago-Abs can be detected in NMOSD and to evaluate its clinical usefulness.
Methods Sera from patients prospectively referred to our centre with suspected NMOSD were tested for AQP4-Abs, MOG-Abs and Ago-Abs with cell-based assays.
Results The cohort included 104 prospective patients: 43 AQP4-Abs-positive cases, 34 MOG-Abs positive cases and 27 double-negative patients. Ago-Abs were detected in 7 of 104 patients (6.7%). Clinical data were available for six of seven patients. The median age at onset of patients with Ago-Abs was 37.5 [IQR 28.8–50.8]; five of six patients tested positive also for AQP4-Abs. Clinical presentation at onset was transverse myelitis in five patients, while one presented with diencephalic syndrome and experienced a transverse myelitis during follow-up. One case presented a concomitant polyradiculopathy. Median EDSS score at onset was 7.5 [IQR 4.8–8.4]; median follow-up was 40.3 months [IQR 8.3–64.7], and median EDSS score at last evaluation was 4.25 [IQR 1.9–5.5].
Conclusion Ago-Abs are present in a subset of patients with NMOSD and, in some cases, represent the only biomarker of an autoimmune process. Their presence is associated with a myelitis phenotype and a severe disease course.
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Contributors JH and RM designed, planned and theorised the study from the beginning and coordinated the collection and analysis of the data as co-last authors.
Funding This work is supported by a public grant overseen by the Agence Nationale de la Recherche (ANR, French research agency) as part of the 'Investissements d’Avenir' programme (ANR-18-RHUS-0012).
Competing interests JH has a patient on anti-Argonaute.
Provenance and peer review Not commissioned; externally peer reviewed.