Anti-SAE autoantibody in dermatomyositis: original comparative study and review of the literature

Among specific autoantibodies in dermatomyositis, the anti-SAE antibody is rare. We aim to describe clinical characteristics, cancer prevalence, and muscle pathology of anti-SAE positive dermatomyositis.Patients with a diagnosis of dermatomyositis and sera positive for the anti-SAE antibody were recruited from 19 centers in this retrospective observational study. Available muscular biopsies were reviewed. We conducted comparison to anti-SAE negative dermatomyositis and a review of the literature.Patients (n = 49) were 84% women. Skin involvement was typical in 96%, with 10% calcinosis, 18% ulceration, 12% necrosis; 35% presented with a widespread skin rash. Muscular disease concerned 84% of patients, with mild weakness (MRC-scale 4 (3; 5)), although with 39% of dysphagia. Muscular biopsies showed typical DM lesions. Interstitial lung disease was found in 21%, mainly of organizing pneumonia pattern, 26% of patients showed dyspnea. Cancer associated-myositis was diagnosed in 16% and responsible for the majority of deaths, its prevalence is five times that of the general population. Intravenous immunoglobulin therapy was administered to 51% of patients during course evolution. Comparison to anti-SAE negative dermatomyostis (n = 85) show less and milder muscle weakness (p= 0.02 and p= 0.006 respectively), lower creatinine kinase levels (p< 0.0001), less dyspnea (p= 0.003).Anti-SAE positive dermatomyositis is a rare subgroup associated with typical skin features but a potentially diffuse rash, a mild myopathy. Interstitial lung disease defines an organizing pneumonia pattern. Cancer associated dermatomyositis prevalence is five times that of the general population.ClinicalTrials.gov, https://clinicaltrials.gov/, NCT04637672.