IFIH1 and Arthritis: The clinical manifestations of disease can be clustered in three main phenotypic subgroups, each one with a different prognosis: anti-MDA5+ rheumatic DM (skin lesions with arthralgia/arthritis) with good prognosis; anti-MDA5+ vasculopathic DM (skin vasculopathy and Raynaud’s phenomenon) with intermediate prognosis; anti-MDA5+ RP-ILD DM, with a prevalence from 50 to 100% and the poorest prognosis and high early mortality (8, 11).