DM: dermatomyositis; PM: polymyositis; IMNM: immune-mediated necrotizing myopathy; IBM: Inclusion body myositis; IIM: idiopathic inflammatory myopathy; MMT: manual muscle testing; anti-ARS: anti-aminoacyl-transfer RNA synthetase; anti-MDA5: anti-melanoma differentiation-associated gene 5; anti-TIF1-γ: anti-transcription intermediary factor 1-γ; CTDs: connective tissue diseases. The gene discussed is IFIH1; the disease is polymyositis.