IFIH1 and dermatomyositis: MDA5+DM is a unique subtype of DM associated with RP-ILD and high mortality.[1,2] In addition, the etiology and pathogenesis remain elusive and the treatment is largely empirical.[7,8,15] Dysregulation of the T cell compartment is implicated in this disease,[9,10,13,14] but direct evidence is largely lacking.