Anti-melanoma differentiation-associated 5 gene antibody-positive dermatomyositis exhibit three clinical phenotypes with different prognoses.

Objectives: We aimed to identify different subtypes of dermatomyositis (DM) patients positive with anti-melanoma differentiation-associated gene 5 antibody (DM-MDA5+) for customised treatments to improve the outcomes.
Methods: Among 96 DM-MDA5+ patients, subgroups with similar phenotypes were delineated using hierarchical clustering analysis of the clinico-biological characteristics. Classification and regression trees were used to build a classification model and survival analysis was used to evaluate the prognoses of subgroups.
Results: Three subgroups were identified among 96 DM-MDA5+ patients, and patients in different subgroups had highly heterogenic manifestations and outcomes. Cluster 1 patients were referred to as mild group of rheumatologic patterns with good prognosis. Cluster 2 patients were referred to as young typical DM group with good prognosis. Cluster 3 patients were referred to as elderly rapidly progressive interstitial lung disease (RPILD) group with poor prognosis. A predictive model to classify patients was established, and three critical factors were found, including age, serum ferritin and myalgia.
Conclusions: DM-MDA5+ patients have a poor short-term prognosis. Three clinical phenotypes with different prognoses were identified in DM-MDA5+ patients.