Immune Mediated Necrotizing Myopathy: Where do we Stand?

Immune-mediated necrotizing myopathies (IMNMs) are a group of acquired autoimmune muscle disorders which are characterized by proximal muscle weakness, high levels of creatinine kinase, and myopathic findings on electromyogram (EMG). Muscle biopsy in IMNM differentiates it from the other subgroups of Idiopathic Inflammatory Myositis (IIM) by the presence of myofibre necrosis and prominent regeneration without substantial lymphocytic inflammatory infiltrates. Anti-signal recognition particle (SRP) and anti-3hydroxy-3 methylglutarylcoenzyme A reductase (HMGCR) autoantibodies were found in two-thirds of IMNM patients. In terms of treatment, IMNM is more resistant to conventional immunosuppressive treatment, therefore, other modalities of treatment such as Intravenous Immunoglobulin (IVIG) and rituximab are often required.