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Summary: There is an unmet need for objective disease-specific biomarkers in the heterogeneous autoimmune neuromuscular disorder myasthenia gravis (MG). This cross-sectional study identified a signature of 23 inflammatory serum proteins with proximity extension assay (PEA) that distinguishes acetylcholine receptor antibody seropositive (AChR+) MG patients from healthy controls (HCs). CCL28, TNFSF14, 4E-BP1, transforming growth factor alpha (TGF-α), and ST1A1 ranked top biomarkers. TGF-β1 and osteoprotegerin (OPG) differed between early- and late-onset MG, whereas CXCL10, TNFSF14, CCL11, interleukin-17C (IL-17C), and TGF-α differed significantly with immunosuppressive treatment. MG patients with moderate to high disease severity had lower uPA. Previously defined MG-associated microRNAs, miR-150-5p, miR-30e-5p, and miR-21-5p, correlated inversely with ST1A1 and TNFSF14. The presented inflammatory proteins that distinguish AChR+ MG are promising serum biomarkers for validation in prospective studies to allow for molecular signatures for patient subgroup stratification and monitoring of treatment response.

IntroductionOur aim was to translate, adapt and validate the Myasthenia Gravis Activities of Daily Living scale into the Latvian language and to evaluate this instrument (MG-ADL-L) in terms of construct validity and reliability.MethodsWe enrolled patients with a confirmed MG diagnosis, who could speak Latvian fluently. We performed translation and adaptation according to the cross-cultural adaptation guidelines for self-reported measures. The patients were evaluated by a physician according to the Myasthenia Gravis Foundation of America classification (MGFA) and using the Myasthenia Gravis Composite Score (MGCS). Patients were asked to complete the MG-ADL-L and the 15-item Myasthenia Gravis Quality of Life (MGQOL15) Internal consistency was evaluated based on Cronbach’s α, reproducibility—Cohen’s weighted kappa and construct validity—Spearman’s correlation between the MG-ADL-L and the MGQOL15 and MGCS. We used the Kruskal–Wallis H test to compare the MG-ADL-L score distribution between the MGFA groups.Results38 enrolled patients in the study. There was an acceptable internal consistency (Cronbach’s α = 0.76) and moderate to very good agreement between the test and retest scores (Cohen’s weighted kappa = 0.54 and 0.81). The MG-ADL-L showed a moderate positive correlation with the MGQOL15 (r = 0.5, p = 0.001) and the MGCS (r = 0.62, p