[Immune-Mediated Necrotizing Myopathy: IMNM]

Immune-mediated necrotizing myopathy (IMNM) is a heterogeneous disease that presents with subacute progressive proximal dominant muscle weakness clinically and prominent necrotic muscle fibers without invasion of inflammatory cells pathologically. IMNM is a disease that exclusively affects skeletal muscles, so the serum creatine kinase level usually increases prominently. It is thought to be an autoimmune disease because of the presence of two autoantibodies, anti-SRP and anti-HMGCR. Because muscle involvement is more severe than that in other forms of myositis, its functional prognosis is worse. Several immune-modifying therapies can improve the symptoms; therefore, intensive treatments should be started soon after diagnosis with IMNM.