Objectives To investigate the histopathological features of the temporalis muscle (TM) and adjacent nerve tissue in active cranial giant cell arteritis (C-GCA). Methods Temporal artery biopsy (TAB) specimens containing fragments of the TM from patients with active C-GCA fulfilling the 2022 ACR/EULAR classification criteria (n = 11) were assessed by conventional histology and immunohistochemistry in comparison with non-GCA controls (n = 3). Clinical, laboratory and imaging features based on patient charts at time of biopsy were retrospectively recorded. Results The majority of the studied TAB specimens showed inflammation of the TM (10/11) and adjacent nerve fascicles (7/11) that was characterized by prominent endomysial lymphomonocytic infiltrates, whereas controls showed no inflammatory lesions and no disruption of the local architecture. Association of active C-GCA with sarcolemmal MHC class I (8/8) and MHC class II (6/11) upregulation suggests primary inflammation of the TM in a subset of patients. αB-Crystallin positivity (10/11) highlights areas of pre-necrotic myofibres within the TM. The presence of endomysial fibrosis, signs of atrophy and variations of muscle fibre size suggest a rather longstanding and potentially subclinical process of myoinflammation. Conclusion Our results expand the spectrum of inflammatory lesions known to be associated with active C-GCA. Specifically, inflammatory infiltration of the TM and adjacent nerve structures could contribute to localized symptoms of the temporomandibular region and may be included in future concepts of pathophysiology.

中文翻译：

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巨细胞动脉炎中颞肌和邻近神经组织的炎症：扩大炎性病变的范围


目的 探讨活动性颅巨细胞动脉炎 （C-GCA） 患者颞肌 （TM） 和邻近神经组织的组织病理学特征。方法 通过常规组织学和免疫组织化学与非 GCA 对照 （n = 3） 进行比较，评估来自符合 2022 年 ACR/EULAR 分类标准 （n = 11） 的活动性 C-GCA 患者的颞动脉活检 （TAB） 标本，其中包含 TM 片段。回顾性记录活检时基于患者病历的临床、实验室和影像学特征。结果 大多数研究的 TAB 标本显示 TM （10/11） 和邻近神经束 （7/11） 的炎症，其特征是明显的肌内膜淋巴单核细胞浸润，而对照组显示无炎症病变，局部结构无破坏。活动性 C-GCA 与肌膜 MHC I 级 （8/8） 和 MHC II 级 （6/11） 上调的关联表明一部分患者的 TM 原发性炎症。αB-晶状体蛋白阳性 （10/11） 突出了 TM 内坏死前肌纤维的区域。肌内膜纤维化、萎缩迹象和肌纤维大小变化的存在表明肌炎的相当长期且潜在的亚临床过程。结论 我们的结果扩大了已知与活动性 C-GCA 相关的炎症病变的范围。具体来说，TM 和邻近神经结构的炎性浸润可能导致颞下颌区的局部症状，并可能包含在未来的病理生理学概念中。