Abstract：
OBJECTIVE: Systemic amyloidosis is a condition in which misfolded amyloid fibrils are deposited within tissues. Amyloid myopathy is a rare manifestation of systemic amyloidosis. However, whether skeletal muscle involvement is underestimated and whether such deposition guarantees clinical and pathological myopathic features remain to be investigated.
METHODS: We retrospectively reviewed patients with systemic amyloidosis, in whom skeletal muscle biopsies were performed at our centre between January 2018 and June 2023. In total, 28 patients with suspected systemic amyloidosis were included. Among these, 21 presented with cardiomyopathy but lacked myopathic symptoms. The clinical and pathological data of these patients were further analysed. The amyloid type was confirmed by immunohistochemistry.
RESULTS: Twenty-eight patients with suspected systemic amyloidosis underwent muscle biopsy. Amyloid deposition in the skeletal muscle was confirmed in 24 patients, including 22 with light-chain amyloidosis (AL) and two with transthyretin amyloidosis (ATTR). Among the 24 patients, seven presented with muscle weakness and decreased muscle strength (Group 1, symptomatic myopathy), whereas the remaining 17 exhibited normal muscle strength (Group 2, asymptomatic myopathy). Group 1 included four patients with AL-λ, one with AL-κ and two with ATTR. Group 2 included 15 patients with AL-λ and two patients with AL-κ. In Group 1, six patients exhibited neuropathy, whereas only one patient in Group 2 presented with subclinical neuropathy on nerve conduction studies. Amyloid deposition in the interstitium was the most obvious change, observed in all 24 patients. Neuropathic changes, including denervation atrophy and muscle fibre grouping, were also common. Except for type 2 fibre atrophy, the other myopathic changes were mild and nonspecific. No sarcolemmal disruption was observed. Immunohistochemical analysis revealed marked positivity for MAC and MHC1 expression in the regions with amyloid deposits. Clinicopathological analysis revealed no significant differences in the extent of muscular amyloid deposition between the two groups. Nevertheless, patients in Group 1 displayed more pronounced neurogenic atrophy on skeletal muscle biopsies.
CONCLUSIONS: Our study indicates that amyloid deposition in skeletal muscle is commonly observed but rarely causes symptomatic myopathy in systemic amyloidosis.
METHODS: We retrospectively reviewed patients with systemic amyloidosis, in whom skeletal muscle biopsies were performed at our centre between January 2018 and June 2023. In total, 28 patients with suspected systemic amyloidosis were included. Among these, 21 presented with cardiomyopathy but lacked myopathic symptoms. The clinical and pathological data of these patients were further analysed. The amyloid type was confirmed by immunohistochemistry.
RESULTS: Twenty-eight patients with suspected systemic amyloidosis underwent muscle biopsy. Amyloid deposition in the skeletal muscle was confirmed in 24 patients, including 22 with light-chain amyloidosis (AL) and two with transthyretin amyloidosis (ATTR). Among the 24 patients, seven presented with muscle weakness and decreased muscle strength (Group 1, symptomatic myopathy), whereas the remaining 17 exhibited normal muscle strength (Group 2, asymptomatic myopathy). Group 1 included four patients with AL-λ, one with AL-κ and two with ATTR. Group 2 included 15 patients with AL-λ and two patients with AL-κ. In Group 1, six patients exhibited neuropathy, whereas only one patient in Group 2 presented with subclinical neuropathy on nerve conduction studies. Amyloid deposition in the interstitium was the most obvious change, observed in all 24 patients. Neuropathic changes, including denervation atrophy and muscle fibre grouping, were also common. Except for type 2 fibre atrophy, the other myopathic changes were mild and nonspecific. No sarcolemmal disruption was observed. Immunohistochemical analysis revealed marked positivity for MAC and MHC1 expression in the regions with amyloid deposits. Clinicopathological analysis revealed no significant differences in the extent of muscular amyloid deposition between the two groups. Nevertheless, patients in Group 1 displayed more pronounced neurogenic atrophy on skeletal muscle biopsies.
CONCLUSIONS: Our study indicates that amyloid deposition in skeletal muscle is commonly observed but rarely causes symptomatic myopathy in systemic amyloidosis.
摘要：
目的：系统性淀粉样变性是一种错误折叠的淀粉样原纤维在组织内沉积的病症。淀粉样肌病是系统性淀粉样变性的罕见表现。然而,骨骼肌受累是否被低估，以及这种沉积是否能保证临床和病理性肌病特征仍有待研究。
方法：我们回顾了系统性淀粉样变性患者，2018年1月至2023年6月在我们中心进行了骨骼肌活检.总的来说,包括28例疑似系统性淀粉样变性患者。其中,21例出现心肌病，但缺乏肌病症状。进一步分析这些患者的临床和病理资料。通过免疫组织化学证实淀粉样蛋白类型。
结果：28例疑似系统性淀粉样变性患者接受了肌肉活检。在24例患者中证实了骨骼肌中的淀粉样蛋白沉积，包括22例轻链淀粉样变性（AL）和2例甲状腺素运载蛋白淀粉样变性（ATTR）。在24名患者中，7例表现为肌肉无力和肌肉力量下降（第1组，症状性肌病），而其余17人表现出正常的肌肉力量（第2组，无症状肌病）。第一组包括四名AL-λ患者，一个带有AL-κ，两个带有ATTR。第2组包括15例AL-λ患者和2例AL-κ患者。在第1组中，有6名患者出现神经病变，而第2组只有1例患者在神经传导研究中出现亚临床神经病变.间质中的淀粉样蛋白沉积是最明显的变化，在所有24名患者中观察到。神经病变,包括去神经萎缩和肌纤维分组，也很常见。除了2型纤维萎缩,其他肌病改变为轻度和非特异性.没有观察到肌膜破坏。免疫组织化学分析显示在具有淀粉样蛋白沉积物的区域中MAC和MHC1表达显著阳性。临床病理分析显示，两组之间的肌肉淀粉样蛋白沉积程度无显着差异。然而，第1组患者在骨骼肌活检中表现出更明显的神经源性萎缩.
结论：我们的研究表明，在系统性淀粉样变性中，通常观察到骨骼肌中淀粉样蛋白沉积，但很少引起症状性肌病。
方法：我们回顾了系统性淀粉样变性患者，2018年1月至2023年6月在我们中心进行了骨骼肌活检.总的来说,包括28例疑似系统性淀粉样变性患者。其中,21例出现心肌病，但缺乏肌病症状。进一步分析这些患者的临床和病理资料。通过免疫组织化学证实淀粉样蛋白类型。
结果：28例疑似系统性淀粉样变性患者接受了肌肉活检。在24例患者中证实了骨骼肌中的淀粉样蛋白沉积，包括22例轻链淀粉样变性（AL）和2例甲状腺素运载蛋白淀粉样变性（ATTR）。在24名患者中，7例表现为肌肉无力和肌肉力量下降（第1组，症状性肌病），而其余17人表现出正常的肌肉力量（第2组，无症状肌病）。第一组包括四名AL-λ患者，一个带有AL-κ，两个带有ATTR。第2组包括15例AL-λ患者和2例AL-κ患者。在第1组中，有6名患者出现神经病变，而第2组只有1例患者在神经传导研究中出现亚临床神经病变.间质中的淀粉样蛋白沉积是最明显的变化，在所有24名患者中观察到。神经病变,包括去神经萎缩和肌纤维分组，也很常见。除了2型纤维萎缩,其他肌病改变为轻度和非特异性.没有观察到肌膜破坏。免疫组织化学分析显示在具有淀粉样蛋白沉积物的区域中MAC和MHC1表达显著阳性。临床病理分析显示，两组之间的肌肉淀粉样蛋白沉积程度无显着差异。然而，第1组患者在骨骼肌活检中表现出更明显的神经源性萎缩.
结论：我们的研究表明，在系统性淀粉样变性中，通常观察到骨骼肌中淀粉样蛋白沉积，但很少引起症状性肌病。
