Review: Immune‐mediated necrotizing myopathies – a heterogeneous group of diseases with specific myopathological features

Abstract

Immune-mediated necrotizing myopathies (IMNMs) are now well recognized among the so-called idiopathic inflammatory myopathies (IIMs), which also comprise dermatomyositis (DM), polymyositis (PM), sporadic inclusion body myositis (sIBM) and non-specific myositis. All of these conditions are defined on the basis of distinct clinical symptoms, in combination with results derived from muscle biopsy and additional data, such as measurement of the serum creatine kinase (CK) level as well as myositis-associated and myositis-specific autoantibodies, electromyography (EMG) and modern imaging techniques. Importantly, diagnosis of one of the above mentioned myositis forms implies a specific clinical syndrome or a distinct disease. However, there is considerable clinical heterogeneity, and overlap requiring further diagnostic precision. Classification and subclassification of IIMs are highly debated and the subjects of intense research, especially as clinical trials with anti-inflammatory agents should follow universally defined and accepted criteria. This review focuses on the description of the spectrum of immune-mediated necrotizing myopathies with an emphasis on their myopathological features.

Treatment and outcomes in necrotising autoimmune myopathy: An Australian perspective

“…All patients were initially referred to our clinic with a symmetrical proximal muscle weakness and a significantly elevated CK level, in keeping with the presentation findings of previous studies [1][2][3][4][5]10,12,14]. In our anecdotal experience, these patients also often have muscle atrophy at presentation, in comparison to the other inflammatory myopathy patients, where this is not commonly seen.…”

“…Muscle biopsy findings in NAM generally show necrotic and regenerating fibres with minimal inflammatory infiltrate, and no evidence of vasculitis [10,11].…”

Inflammatory Muscle Diseases

“…3,4,6,[14][15][16] Most patients with necrotizing autoimmune myositis have antibodies against signal recognition particle (SRP) or against 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) (see the Glossary). [14][15][16] …”

Immunotherapies for Immune-Mediated Myopathies: A Current Perspective

“…The best-characterized subgroups are those associated with serum autoantibodies to signal recognition peptide (anti-SRP), or to 3-hydroxy-3-methyl-glutaryl-CoA reductase (anti-HMGCR), the latter usually occurring in patients who have been on statin drugs, but may also occur in statin-naïve patients. NAM may also occur in the absence of these antibodies in patients with malignancy, connective tissue diseases, or viral infections [29]. The inflammatory infiltrate is usually absent or sparse but when present comprises mainly CD68+ macrophages, with a type I helper T cell (Th1)/M1 macrophage response in the muscle tissue [30].…”