特发性炎症性肌病 (IIM) 是一组异质性全身性自身免疫性疾病，影响骨骼肌，也可能累及皮肤、关节、肺和心脏。由于分类标准的变化以及使用医疗记录诊断编码进行病例识别的固有缺陷，IIM 的流行病学变得模糊。 IIM 的发病率估计为每 100,000 人年 0.2 至 2 例，患病率为每 100,000 人 2 至 25 例。尽管年龄和性别对发病率的影响众所周知，但对种族差异（尤其是土著居民）的了解却很少。据报道，IIM 的发病率在 21 世纪有所增加，但尚不清楚这是否是真正的增加。对不同 IIM 亚型的遗传风险因素的了解已取得很大进展。感染、药物、恶性肿瘤和地理位置也是常见的危险因素。 COVID-19 大流行可能改变了 IIM 的发病率，尽管这种情况的证据仅限于病例报告和小病例系列。考虑当前对 IIM 流行病学的理解可以突出未来研究这些罕见疾病的重要领域。© 2023。Springer Nature Limited。

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of systemic autoimmune diseases that affect the skeletal muscles and can also involve the skin, joints, lungs and heart. The epidemiology of IIM is obscured by changing classification criteria and the inherent shortcomings of case identification using healthcare record diagnostic coding. The incidence of IIM is estimated to range from 0.2 to 2 per 100,000 person-years, with prevalence from 2 to 25 per 100,000 people. Although the effects of age and gender on incidence are known, there is only sparse understanding of ethnic differences, particularly in indigenous populations. The incidence of IIM has reportedly increased in the twenty-first century, but whether this is a genuine increase is not yet known. Understanding of the genetic risk factors for different IIM subtypes has advanced considerably. Infections, medications, malignancy and geography are also commonly identified risk factors. Potentially, the COVID-19 pandemic has altered IIM incidence, although evidence of this occurrence is limited to case reports and small case series. Consideration of the current understanding of the epidemiology of IIM can highlight important areas of interest for future research into these rare diseases.© 2023. Springer Nature Limited.