Clinical Significance of Myositis-Specific and Myositis-Associated Antibody Profiles in Dermatomyositis.

Abstract

Myositis-specific autoantibodies (MSA) and myositis-associated autoantibodies (MAA) are clinically useful biomarkers that point to the diagnosis, clinical manifestations, and prognosis of dermatomyositis (DM). To estimate the prevalence of MSA as well as MAA and analyze possible clinical correlations of these autoantibodies in patients diagnosed with DM, we conducted a cross-sectional study of 30 patients who were diagnosed with DM. MSA were positive in 19 patients (63%) in which Mi 2 was positive in 8 (27%) patients, and this was the most frequently found MSA. A total of 11 (36.7%) patients showed positive MAA. AntiPM/Scl 75 and anti-Ro 52 were positive in 5 (16.7%) patients each and these were the most commonly found MAA. Anti-La was absent in all our patients. There were 8 (27%) patients in whom both MSA and MAA were positive. Either MSA and/or MAA were positive in 22 (73%) patients. On a bivariate analysis, the patients who were positive for anti-PM/Scl 75 showed a significant difference in manifesting cutaneous ulcers (P value 0.023). It was also found that anti-SAE-positive patients showed a significant difference with malignancy (P value 0.014). Anti-Ro 52-positive patients were less likely to have symmetrical proximal muscle weakness (P value 0.006). All patients who were anti-MDA 5 positive had myositis and none of the anti-MDA 5-positive patients had rapidly progressive interstitial lung disease (RPILD). More than one MSA in the same patient was noted in three patients.