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Factors associated with endomysial fibrosis in anti-signal recognition particle antibody immune-mediated necrotising myopathy
J. Yuan1, M. Yang2, Y. Zheng3, H. Hao4, F. Gao5, W. Zhang6, Z. Wang7, Y. Yuan8, Y. Zhao9
- Department of Neurology, Peking University First Hospital, Beijing, China.
- Department of Neurology, Peking University First Hospital, Beijing; and Department of Neurology, Beijing Jishuitan Hospital, Capital Medical University, Beijing, China.
- Department of Neurology, Peking University First Hospital, Beijing, China.
- Department of Neurology, Peking University First Hospital, Beijing, China.
- Department of Neurology, Peking University First Hospital, Beijing, China.
- Department of Neurology, Peking University First Hospital, Beijing, China.
- Department of Neurology, Peking University First Hospital, Beijing; Beijing Key Laboratory of Neurovascular Disease Discovery, Beijing; and Rare Disease Medical Center, Peking University First Hospital, Beijing, China.
- Department of Neurology, Peking University First Hospital, Beijing; Beijing Key Laboratory of Neurovascular Disease Discovery, Beijing; and Rare Disease Medical Center, Peking University First Hospital, Beijing, China.
- Department of Neurology, Peking University First Hospital, Beijing, China. 18813187041@163.com
CER19077
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PMID: 41562357 [PubMed]
Received: 06/07/2025
Accepted : 12/12/2025
In Press: 19/01/2026
Abstract
OBJECTIVES:
Anti-signal recognition particle antibody immune-mediated necrotising myopathy (anti-SRP-IMNM) is characterised by prominent muscle weakness and poor neurological outcomes. This study aimed to evaluate the relationship between endomysial fibrosis and the clinical, muscle magnetic resonance imaging (MRI) and myo-pathological features of patients with anti-SRP-IMNM.
METHODS:
We collected the clinical, imaging, and myo-pathological data of patients diagnosed with anti-SRP-IMNM. Differences between patients with and without increased endomysial fibrosis on muscle biopsy were compared.
RESULTS:
Ninety-four patients were included in the study, comprising 12 paediatric and 82 adult patients. The mean age at onset was 41.2±17.3 years. The mean serum creatinine kinase concentration was 6885.8±6300.7 IU/L. MRI revealed muscle oedema in 87.3% of patients and fatty infiltration in 77.5%, which was particularly severe in the muscles of the posterior thigh. Endomysial fibrosis was found in 50% of patients and was significantly associated with early onset (p=0.004), paediatric age (p=0.044), muscle fatty infiltration on MRI of the thigh (p=0.045), and inflammatory cell infiltration on pathology (p<0.05).
CONCLUSIONS:
In anti-SRP-IMNM, endomysial fibrosis may be the pathological basis of fatty infiltration observed on MRI and may be associated with resistance to immunotherapy.
