Different phenotypes in dermatomyositis associated with anti-MDA5 antibody: Study of 121 cases.

Objectives The predominance of extramuscular manifestations (e.g., skin rash, arthralgia, interstitial lung disease [ILD]) as well as the low frequency of muscle signs in anti–melanoma differentiation-associated gene 5 antibody–positive (anti-MDA5+) dermatomyositis caused us to question the term myositis-specific antibody for the anti-MDA5 antibody, as well as the homogeneity of the disease. Methods To characterize the anti-MDA5+ phenotype, an unsupervised analysis was performed on anti-MDA5+ patients (n = 83/121) and compared to a group of patients with myositis without anti-MDA5 antibody (anti-MDA5−; n = 190/201) based on selected variables, collected retrospectively, without any missing data. Results Within anti-MDA5+ patients (n = 83), 3 subgroups were identified. One group (18.1%) corresponded to patients with a rapidly progressive ILD (93.3%; p Conclusion Anti-MDA5+ patients have a systemic syndrome distinct from other patients with myositis. Three subgroups with different prognosis exist.