HMGCR and idiopathic inflammatory myopathy: Immune-mediated necrotizing myopathy (IMNM) is a recently described subtype of idiopathic inflammatory myopathies (IIMs), which are mainly defined by three subtypes according to different myositis-specific autoantibodies (MSAs), including anti-signal recognition particle (SRP) positive IMNM, anti-3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) positive IMNM, and IMNM with no known autoantibodies (seronegative IMNM) [1].