Objectives-The diagnosis of inclusion body myositis (IBM) can be challenging as it can be difficult to clinically distinguish from other forms of myositis, particularly polymyositis (PM). Recent studies have shown frequent presence of autoantibodies directed against cytosolic 5'-nucleotidase 1A (cN-1A) in patients with IBM. We therefore, examined the autoantigenicity and disease-specificity of major epitopes of cN-1A in patients with sporadic IBM compared with healthy and disease controls.Methods-Serum samples obtained from patients with IBM (n=238), polymyositis (PM) and dermatomyositis (DM) (n=185), other autoimmune diseases (n=246), other neuromuscular diseases (n=93) and healthy controls (n=35) were analysed for the presence of autoantibodies using immunodominant cN-1A peptide enzyme-linked immunosorbent assays (ELISAs).

IntroductionThe aim of this study was to examine the serum levels of S100 proteins and to evaluate their role in patients with recent-onset rheumatoid arthritis (RA).MethodsSerum levels of S100A8/9 and S100A12 were analysed in 43 patients with recent-onset RA, both before and three months after the initiation of conventional treatment, as well as in 32 healthy individuals. Disease activity was assessed based on serum levels of C-reactive protein (CRP), the Disease Activity Score for 28 joints (DAS28) and the total number of swollen joints count for 66 joints (SJC).ResultsThe levels of serum S100A8/9 and S100A12 were significantly higher in patients with recent-onset RA compared to the levels in healthy individuals (P < 0.0001) and normalised after three months of treatment. Using age- and sex-adjusted analysis, S100A8/9 levels were correlated with CRP (r = 0.439, P < 0.01), DAS28 (r = 0.501, P = 0.002) and SJC (r = 0.443, P = 0.007), while S100A12 was less significantly correlated with these parameters. Higher levels of S100A8/9 at baseline predicted improvement in the levels of CRP and SJC over time. Moreover, decreases in serum S100A8/9 were associated with decreased serum levels of CRP (r = 0.459, P = 0.005) and improvements in SJC (r = 0.459, P = 0.005). In multiple linear regression analyses, decreases in S100A8/9 but not CRP were significant predictors for improvements in SJC (P = 0.001).ConclusionsThis study is the first to show normalisation of elevated S100 proteins in patients with recent-onset RA after the initiation of conventional treatment. Therefore, S100A8/9 might potentially be a predictive marker for improvement in the total number of swollen joints in patients in the early phase of RA.

Our data show an increasing incidence of IMNM, which is mainly accounted for by anti-HMGCR-positive IMNM associated with the use of statins.