骨骼肌是人类体内最丰富的组织之一，负责产生运动。肌肉受伤可导致严重残疾。骨骼肌具有重要的再生能力，这是由于肌母细胞与免疫细胞之间的相互作用所致。中性粒细胞作为肌肉损伤的诱导剂和初始炎症反应的促进剂非常重要，最终允许肌肉修复。中性粒细胞的主要功能包括吞噬、呼吸突触、颗粒溶解和中性粒细胞胞外陷阱（NETs）的产生。在肌肉损伤后，中性粒细胞的过度激活可能会导致初始损伤的扩大，并妨碍成功的肌肉修复。中性粒细胞作为诱导肌肉损伤的重要性不仅限于急性肌肉损伤，最近，中性粒细胞在特发性炎性肌病（IIM）等慢性肌肉病的免疫病理发病机制中变得更加重要。这个异质性的全身自身免疫性疾病群的特点是肌肉炎症的存在，并伴有不同程度的肌外表现。在IIM中，中性粒细胞被发现具有作为疾病活动标志物的作用，它们在外周血中的扩增与一些临床特征如间质性肺疾病（ILD）和癌症相关。另一方面，低密度粒细胞（LDG）是一种独特的中性粒细胞亚型，具有增强的NETs产生。这些细胞与NETs也与疾病活动和某些临床特征如ILD、血管病、骨化症、皮病和皮肤溃疡有关。在IIM的免疫病理发病机制中，NETs的作用得到了支持，这是由于在皮肌炎和抗合成酶综合征患者中观察到的NET产生增强和NET降解不足。最后，另一种LDG表型的研究引起了新的兴趣，该表型对应于骨髓源性抑制细胞，这些细胞也被发现在IIM患者中扩增，并与疾病活动相关。在本综述中，我们讨论了中性粒细胞既是肌肉修复的组织指挥者又是肌肉损伤的诱导物的作用，并重点讨论IIM的免疫病理发病机制。版权所有 ©2023年Torres-Ruiz，Alcalá-Carmona，Alejandre-Aguilar和Gómez-Martín。

Skeletal muscle is one of the most abundant tissues of the human body and is responsible for the generation of movement. Muscle injuries can lead to severe disability. Skeletal muscle is characterized by an important regeneration capacity, which is possible due to the interaction between the myoblasts and immune cells. Neutrophils are fundamental as inducers of muscle damage and as promoters of the initial inflammatory response which eventually allows the muscle repair. The main functions of the neutrophils are phagocytosis, respiratory burst, degranulation, and the production of neutrophil extracellular traps (NETs). An overactivation of neutrophils after muscle injuries may lead to an expansion of the initial damage and can hamper the successful muscle repair. The importance of neutrophils as inducers of muscle damage extends beyond acute muscle injury and recently, neutrophils have become more relevant as part of the immunopathogenesis of chronic muscle diseases like idiopathic inflammatory myopathies (IIM). This heterogeneous group of systemic autoimmune diseases is characterized by the presence of muscle inflammation with a variable amount of extramuscular features. In IIM, neutrophils have been found to have a role as biomarkers of disease activity, and their expansion in peripheral blood is related to certain clinical features like interstitial lung disease (ILD) and cancer. On the other hand, low density granulocytes (LDG) are a distinctive subtype of neutrophils characterized by an enhanced production of NETs. These cells along with the NETs have also been related to disease activity and certain clinical features like ILD, vasculopathy, calcinosis, dermatosis, and cutaneous ulcers. The role of NETs in the immunopathogenesis of IIM is supported by an enhanced production and deficient degradation of NETs that have been observed in patients with dermatomyositis and anti-synthetase syndrome. Finally, new interest has arisen in the study of other phenotypes of LDG with a phenotype corresponding to myeloid-derived suppressor cells, which were also found to be expanded in patients with IIM and were related to disease activity. In this review, we discuss the role of neutrophils as both orchestrators of muscle repair and inducers of muscle damage, focusing on the immunopathogenesis of IIM.Copyright © 2023 Torres-Ruiz, Alcalá-Carmona, Alejandre-Aguilar and Gómez-Martín.