Autoanticorpi e miopatie infiammatorie

Background. Idiopathic Inflammatory Myopathies (IIMs), also known as myositis, are rare immune-mediated rheumatic diseases that mainly affect skeletal muscle and with possible involvement of multiple organs. The autoantibody profile of IIMs is used to identify clinical phenotype, predict organ manifestations and treatment response. Myositis-specific autoantibodies (MSA) and myositis-associated autoantibodies (MAA) are the two categories of autoantibodies found in IIMs. Antibodies directed against the dense fine speckled 70 kD target antigen (DFS70) have a low prevalence in autoimmune rheumatic diseases, and few studies have investigated the presence of anti-DFS70 antibodies in myositis. Objectives. This study aimed to characterize the autoantibody profile, establish differences in autoantibody expression in different subtypes of IIMs, and measure the prevalence of anti-DFS-70 antibodies. The study also aimed to verify the clinical utility of autoantibody profiling by analyzing correlations with clinical manifestations, malignancy history, and presence of anti-DFS-70 antibodies. Methods. Consecutive patients with myositis were evaluated for the study. Anti-DFS70ab pattern was determined by indirect immunofluorescence on HEp-2000 cells. Detection of anti-DFS70ab specificity, MDA-5, TIF1-γ, SAE1, SAE2, NXP-2, Jo-1, PL-7, PL-12, EJ, OJ, KS, ZO, HA, SRP, Mi-2, HMGCR, U1-RNP, SSaRo52/60, PMScl100/75, Ku, Scl-70, CENP-A, CENP-B, RNA Polymerase III, Th/to, Fibrillarin, Sm, Sm/RNP, SSB/La, PCNA were performed using immunoblotting assay. Clinical, serological, and instrumental data were recorded. Statistical tests such as Student's t-test, Mann-Whitney test, exact Fisher test, one-way ANOVA, and Kruskal-Wallis test were used to analyze the data. Results. During the study period, 39 adult patients with IIMs were examined, and their diagnoses were as follows: dermatomyositis (n=15), polymyositis (n=9), overlap syndrome (n=11), and antisynthetase syndrome (n=4). Serum MSA or MAA antibodies were found in 25/39 patients (64.1%). Among MSA, anti-Jo-1 was present in 6 patients (15.4%); anti-Mi-2 in 5 patients (12.8%); anti-NXP-2 in 4 patients (10.2%) and anti-HMGCR in the only patient with concomitant positivity for anti-PM-Scl100. Among MAA, anti-SSaRo52 antibodies were present in 7 patients (17.9%), anti-SSaRo60 in 5 patients (12.8%), anti-PM-Scl100 in 2 patients (5.1%), anti-Ku in 2 patients (5.1%), and anti-PM-Scl75 in 1 patient (2.6%). ANA antibodies were positive in 28 out of 39 patients (71.8%). Two out of 39 patients with IIMs (5.1%) tested positive for anti-DFS70 antibodies, with one patient exclusively positive and the other positive for both anti-DFS70 and anti-SSaRo60. No significant correlations and differences were found in anti-DFS70 positive patients. 34 patients out of a total of 39 (87.2%) were positive for at least one autoantibody (MSA, MAA, DFS70, ANA, others). Anti-Jo1 antibodies, were significantly associated with interstitial lung disease (p= 0.0003), and arthritis (p= 0.0294). Anti-Mi2 antibodies, were significantly associated with the presence of abnormalities in capillaroscopy (p= 0.0519). 2 cases (5.1%) of malignancies were found, specifically 2 melanomas in 2 patients with PM and both positive for both anti-Jo1 and anti-SSaRo52 antibodies. Conclusions. This study demonstrated the clinical utility of autoantibody profiling in IIMs patients and its correlation with clinical manifestations, malignancy history, and the high prognostic value of autoantibody profiling in these patients. Anti-Jo-1 and anti-SSaRo52 were the most common MSA and MAA found in IIMs patients. The results showed low prevalence of anti-DFS70 antibodies in IIMs patients, consistent with previous studies. These findings provides insight into the clinical utility of autoantibody profiling and could help to identify areas for future research for the pathophysiology, the diagnosis and for individualized treatment of IIMs.