IFIH1 and Arthritis: MDA5+ DM clinical manifestations can be clustered in three main subgroups: anti-MDA5+ rheumatic DM with skin lesions and/or arthralgia/arthritis; anti-MDA5+ vasculopathic DM, characterized by skin vasculopathy and Raynaud’s phenomenon; anti-MDA5+ RP-ILD DM, with a prevalence of 50-100%, characterized by poor prognosis and high early mortality (8, 11).