The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of diseases, collectively termed myositis, sharing symptoms of muscle weakness, fatigue and inflammation. Other organs are frequently involved, supporting the notion that these are systemic inflammatory diseases. The IIMs can be subgrouped into dermatomyositis, polymyositis and inclusion body myositis. The myositis-specific autoantibodies (MSAs) identify other and often more distinct clinical phenotypes, such as the antisynthetase syndrome with antisynthetase autoantibodies and frequent interstitial lung disease and anti-SRP and anti-HMGCR autoantibodies that identify necrotizing myopathy. The MSAs are important both to support myositis diagnosis and to identify subgroups with different patterns of extramuscular organ involvement such as interstitial lung disease. Another cornerstone in the diagnostic procedure is muscle biopsy to identify inflammation and to exclude noninflammatory myopathies. Treatment effect and prognosis vary by subgroup. To develop new and better therapies, validated classification criteria that identify distinct subgroups of myositis are critical. The lack of such criteria was the main rationale for the development of new classification criteria for IIMs, which are summarized in this review; the historical background regarding previous diagnostic and classification criteria is also reviewed. As the IIMs are rare diseases with a prevalence of 10 in 100 000 individuals, an international collaboration was essential, as was the interdisciplinary effort including experts in adult and paediatric rheumatology, neurology, dermatology and epidemiology. The new criteria have been developed based on data from more than 1500 patients from 47 centres worldwide and are based on clinically easily available variables.

中文翻译：

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特发性炎症性肌病的诊断和分类。

特发性炎症性肌病（IIM）是一组异类疾病，统称为肌炎，具有肌肉无力，疲劳和发炎的症状。其他器官也经常参与其中，支持了这些是全身性炎症性疾病的观点。IIM可分为皮肌炎，多肌炎和包涵体肌炎。肌炎特异性自身抗体（MSA）可以识别其他且通常更独特的临床表型，例如具有抗合成酶自身抗体的抗合成酶综合征和频繁的间质性肺疾病以及识别坏死性肌病的抗SRP和抗HMGCR自身抗体。MSA对支持肌炎诊断和鉴定具有不同类型的肌外器官受累模式（例如间质性肺病）的亚组都很重要。诊断过程中的另一个基石是肌肉活检，以识别炎症并排除非炎症性肌病。治疗效果和预后因亚组而异。为了开发新的更好的疗法，确定肌炎不同亚组的有效分类标准至关重要。缺乏此类标准是制定IIM新分类标准的主要理由，本综述对此进行了总结。还回顾了有关先前诊断和分类标准的历史背景。由于IIM是罕见病，每10万人中有10人患病，因此开展国际合作至关重要，包括成人和小儿风湿病，神经病学，皮肤病学和流行病学专家在内的跨学科研究也至关重要。