Abstract
Background Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) defines a distinct demyelinating disorder. The clinical relevance of MOG-immunoglobulin G (MOG-IgG) in cerebrospinal fluid (CSF) without corresponding seropositivity (CSF-restricted MOG-IgG) remains unclear.
Methods The national diagnostic and clinical database for the Australasian MOGAD Study Group was reviewed from 2018 to 2024. Patients were diagnosed as MOG-IgG positive in serum or CSF using a flow cytometry live cell-based assay.
Results Over six years of testing in a national referral centre, 1127 patients had paired CSF and serum samples tested. 59/111 (53.2%) of CSF samples in seropositive patients demonstrated concurrent CSF positivity for MOG-IgG, while 52/111 (46.8%) seropositive patients were antibody-negative in paired CSF. 1009/1016 (99.3%) seronegative patients were negative in paired CSF samples, and 7/1016 (0.7%) of seronegative cases had a CSF-restricted MOG-IgG profile. Of these seven patients, four had an alternate diagnosis confirmed, including three with multiple sclerosis and one with central nervous system vasculitis. The remaining 3/7 patients presented with longitudinally extensive transverse myelitis, classified as a high-risk phenotype for MOGAD, although one was diagnosed with a likely parainfectious myelitis and another as transverse myelitis associated with Sjogren’s syndrome.
Conclusion A CSF-restricted MOG-IgG profile is rare, with over half of these patients having an alternate non-MOGAD diagnosis confirmed. We strongly recommend the use of serum as the biospecimen of preference in testing for MOG IgG. We additionally urge caution in the interpretation of CSF-restricted MOG-IgG in unselected patients who do not have clinical, radiological or ancillary investigations consistent with MOGAD.