Idiopathic inflammatory myopathies (IIM) are connective tissue diseases (CTD) that involve muscle with varying severity [1]. They include polymyositis, dermatomyositis, overlap myositis, inclusion body myositis, and immune-mediated necrotizing myopathies (IMNM). IMNM is characterized by muscle fiber necrosis and myophagocytosis without frequent lymphocytic infiltrates. Based on associated antibodies, subtypes are classified into IMNM with two positive myositis-specific autoantibodies (MSAs), anti-SRP (signal recognition particle) or anti-HMGCR antibodies, and seronegative IMNM [1,2].
