Comparison of clinical features between patients with anti-synthetase syndrome and dermatomyositis: results from the MYONET registry

Abstract

Objectives: To compare clinical characteristics, including the frequency of cutaneous, extramuscular manifestations and malignancy, between adults with anti-synthetase syndrome (ASyS) and DM. Methods: Using data regarding adults from the MYONET registry, a cohort of DM patients with anti-Mi2/-TIF1c/-NXP2/-SAE/-MDA5 autoantibodies, and a cohort of ASyS patients with anti-tRNA synthetase autoantibodies (anti-Jo1/-PL7/-PL12/-OJ/-EJ/-Zo/-KS) were identified. Patients with DM sine dermatitis or with discordant dual autoantibody specificities were excluded. Sub-cohorts of patients with ASyS with or without skin involvement were defined based on presence of DM-type rashes (heliotrope rash, Gottron’s papules/sign, violaceous rash, shawl sign, V-sign, erythroderma, and/or periorbital rash). Results: In total 1054 patients were included (DM, n ¼ 405; ASyS, n ¼ 649). In the ASyS cohort, 31% (n ¼ 203) had DM-type skin involvement (ASyS-DMskin). A higher frequency of extramuscular manifestations, including Mechanic’s hands, Raynaud’s phenomenon, arthritis, interstitial lung disease and cardiac involvement differentiated ASyS-DMskin from DM (all P < 0.001), whereas higher frequency of any of four DM-type rashes—heliotrope rash (n ¼ 248, 61% vs n ¼ 90, 44%), violaceous rash (n ¼ 166, 41% vs n ¼ 57, 9%), V-sign (n ¼ 124, 31% vs n ¼ 28, 4%), and shawl sign (n ¼ 133, 33% vs n ¼ 18, 3%)—differentiated DM from ASyS-DMskin (all P < 0.005). Cancer-associated myositis (CAM) was more frequent in DM (n ¼ 67, 17%) compared with ASyS (n ¼ 21, 3%) and ASyS-DMskin (n ¼ 7, 3%) cohorts (both P < 0.001). Conclusion: DM-type rashes are frequent in patients with ASyS; however, distinct clinical manifestations differentiate these patients from classical DM. Skin involvement in ASyS does not necessitate increased malignancy surveillance. These findings will inform future ASyS classification criteria and patient management.