Therapeutic Outcomes and Electrophysiological Biomarkers in Anti-Myelin-Associated Glycoprotein Neuropathy: A Multicenter Cohort Study in South Korea

Background and Purpose Unlike other immune-mediated neuropathies, anti-myelin -as-sociated glycoprotein (MAG) neuropathy is often refractory to immunotherapy. It is necessary to compare the relative efficacies of various immunotherapies and develop objective biomark-ers in order to optimize its clinical management.Methods This study recruited 91 patients with high anti-MAG antibody titers from 7 tertiary hospitals in South Korea. We analyzed the baseline characteristics, therapeutic outcomes, and nerve conduction study (NCS) findings of 68 patients and excluded 23 false positive cases.Results The rate of positive responses to treatment was highest using zanubrutinib (50%) and rituximab (36.4%), followed by corticosteroids (16.7%), immunosuppressants (9.5%), in-travenous immunoglobulin (5%), and plasma exchange (0%). Disability and weakness were significantly associated with multiple NCS parameters at the time of diagnosis, especially dis-tal compound muscle action potential (CMAP) amplitudes. Moreover, the longitudinal tra-jectory of the average CMAP amplitudes paralleled the clinical courses, with a 16.2 percentile decrease as an optimal cutoff for predicting a clinical exacerbation (area under the receiver op-erating characteristic curve=0.792).Conclusions Our study supports the use of NCS as an objective marker for estimating disease burden and tracking clinical changes in patients with anti-MAG neuropathy. We have described the beneficial effects of rituximab and a new drug, zanubrutinib, compared with conventional immunotherapies.