Abstract
Idiopathic inflammatory myopathies (IIM) comprise a heterogeneous group of autoimmune muscle diseases with variable patterns of muscle damage. In this multicentric cross-sectional study, we employed scanning electron microscopy (SEM) to characterize ultrastructural alterations in muscle biopsies from quadriceps (n = 29) and deltoid (n = 41) of 70 IIM patients classified by ENMC (European Neuromuscular Centre) 2004/2011/2023 and EULAR/ACR (European League Against Rheumatism / American College of Rheumatology) 2017 criteria, together with 8 control samples. Qualitative assessment revealed loss of hexagonality and fiber size variability across all samples, while porosities, ruptures, perforations, and sarcolemma remnant emerged as candidates to phenotype-specific distribution. Dermatomyositis (DM) presented relatively preserved ultrastructure, immune-mediated necrotizing myopathy (IMNM) exhibited perforations, and inclusion body myositis (IBM) displayed sarcolemma remnant. Perforations were linked to necrosis, whereas fatty replacement was less frequent in samples with ultrastructural alterations. Quantitative morphometry showed higher variability in quadriceps compared with deltoid fibers, and Z-score normalization confirmed widespread myofiber atrophy across IIM subtypes. Building upon previous preliminary observations, this study expands SEM-based analysis to a larger multicentric cohort, revealing preliminary phenotype-specific ultrastructural signatures that may contribute to a better understanding of the pathophysiological mechanisms of muscle damage in IIM.
Data availability
All original images from the scanning electron microscope shown in Fig. 2 are available in: https://doi.org/10.6084/m9.figshare.28942067.
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Acknowledgements
We acknowledge the support of the Secretaría de Ciencias, Humanidades y Tecnologías (SECIHTI) for providing funding for the development of this work through Ciencia de Frontera 2023 (CF-2023-G-1396) to Monica Vazquez-Del Mercado, PhD. We really appreciate to Dr. Ruth Padilla Muñoz for her welcome and support for this research work at the Instituto Transdisciplinar de Investigación y Servicios (ITRANS), Universidad de Guadalajara.
Funding
Dr. Monica Vazquez-Del Mercado received funding from the Secretaría de Ciencia, Humanidades, Tecnología e Innovación (SECIHTI) through Ciencia de Frontera 2023–2025, grant number CF-2023-G-1396.
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**A.A.** contributed with substantial contributions to the conception and design of the work, analysis and interpretation of data, and drafted the work; **C.J.** contributed with substantial contributions to the conception and design of the work, analysis and interpretation of data, and drafted the work; **E.G.** contributed with the design of the work, the acquisition, analysis, and interpretation of data; **G.M.** contributed with the acquisition and interpretation of data, and the design of the work; **S.V.** contributed with the acquisition and interpretation of data, and the design of the work; **A.V.** contributed with the acquisition and interpretation of data; **J.M.G.** contributed with the acquisition of data and drafted the work; **G.T.** contributed with the acquisition and interpretation of data; **C. A. G.** contributed with the acquisition and analysis of data; **J.M.** contributed with the acquisition and interpretation of data; **E.C.** contributed with the design of the work, the analysis and interpretation of data, and drafted the work; **B.M.** contributed with the design of the work, the interpretation of data, and drafted the work; **O.P.** contributed with the design of the work, the interpretation of data, and drafted the work; **E.M.** contributed with the design of the work, the interpretation of data, and drafted the work; **F.P.** contributed with the design of the work, the analysis and interpretation of data, and drafted the work; **F.S.** contributed with the design of the work, the interpretation of data, and drafted the work; **M.S.** contributed with the interpretation of data, and drafted the work; **E.R.** contributed with the interpretation of data, and drafted the work; **J.B.** contributed with the analysis of data and drafted the work; **G.G.** contributed with the analysis of data and drafted the work; **A.G.** contributed with the analysis of data and drafted the work; **A.R.** contributed with the acquisition and interpretation of data; **M.C.** contributed with the acquisition and interpretation of data; **A.Ll.** contributed with the acquisition and interpretation of data; **M.V.** contributed with the conception and design of the work, interpretation of data, and drafted the work.
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Aguilar-Vazquez, A., Juarez-Gomez, C., Gonzalez-Gauna, E. et al. Preliminary ultrastructural analysis suggests phenotype-specific myofiber alterations in idiopathic inflammatory myopathies. Sci Rep (2026). https://doi.org/10.1038/s41598-026-42717-3
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DOI: https://doi.org/10.1038/s41598-026-42717-3
