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Abstract

Necrotizing autoinmune myopathy (NAM) was recognized as a new sub- group of myositis after the observation of necrosis with mild or absent inflam- matory infiltrates in muscle biopsies, in addition of expression of two specific myositis antibodies (antiSRP and antiHMGCR), which are strongly associated to the mentioned hystologic findings, with different clinical phenotypes depending on the presence of each antibody, but sharing some features like severe proximal muscle weakness, significant elevation of creatin phosphokinase (CK), mild ex­tramuscular involvement and resistance to commonly used immunosupressants. The first proposed approach to classification criteria was hystology-based, none- theless the observation of necrosis in some other types of myositis and the homo- geneity of clinical features in patients expressing antiSRP or antiHMGCR despite the hystologic findings led to a new classification scheme leaded by the European Neuromuscular Center in 2016, which recognizes thre different clinical entities of NAM, based on the antibody expression plus the presence of proximal muscle weakness, relying hystology to a secondary place thus eliminating the need for immediate biopsy to stablish a diagnosis: those are antiSRP myopathy, antiHMG- CR myopathy and seronegative necrotizing myopathy, being the last one the only needing muscle biopsy. The present review shows the actual knowledge about NAM and its subtypes, referring to hystoric, clinical, hystologic, immunopatholog- ic, prognostic and therapeutic issues.