Clinical aspects
Polymyositis is a rare and favourable outcome subtype of idiopathic inflammatory myopathy in Chinese patients
C. Sun1, X. Tian2, H. Yang3, H. Yang4, S. Li5, W. Jiang6, Q. Peng7, G. Wang8, X. Lu9
- Peking University, China-Japan Friendship School of Clinical Medicine, Beijing, and Department of Rheumatology, China-Japan Friendship Hospital, Beijing, China.
- Department of Rheumatology, China-Japan Friendship Hospital, Beijing, China.
- Peking University, China-Japan Friendship School of Clinical Medicine, Beijing, and Department of Rheumatology, China-Japan Friendship Hospital, Beijing, China.
- Department of Rheumatology, China-Japan Friendship Hospital, Beijing, China.
- Department of Rheumatology, China-Japan Friendship Hospital, Beijing, China.
- Department of Rheumatology, China-Japan Friendship Hospital, Beijing, China.
- Department of Rheumatology, China-Japan Friendship Hospital, Beijing, China
- Peking University, China-Japan Friendship School of Clinical Medicine, Beijing, and Department of Rheumatology, China-Japan Friendship Hospital, Beijing, China.
- Peking University, China-Japan Friendship School of Clinical Medicine, Beijing, and Department of Rheumatology, China-Japan Friendship Hospital, Beijing, China. luxin_n@163.com
CER17347
2024 Vol.42, N°2
PI 0302, PF 0308
Clinical aspects
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PMID: 38488095 [PubMed]
Received: 02/12/2023
Accepted : 16/02/2024
In Press: 14/03/2024
Published: 14/03/2024
Abstract
OBJECTIVES:
To investigate the prevalence and characteristics of typical polymyositis (PM) in Chinese patients with idiopathic inflammatory myopathy (IIM).
METHODS:
Patients diagnosed with IIM according to the 2017 EULAR/ACR criteria were included. Serological aspects including myositis-specific antibodies (MSA) and pathological data were re-evaluated. The diagnosis of typical PM was strictly done using the pathological criteria, while excluding other IIM subtypes such as dermatomyositis (DM), immune-mediated necrotising myopathies (IMNM), anti-synthetase syndrome (ASS), and sporadic inclusion body myositis (sIBM), based on their respective diagnostic criteria.
RESULTS:
A total of 544 IIM patients with muscle biopsy were involved, and 129 of them were diagnosed with initial PM according to the 2017 EULAR/ACR criteria. Only 6 (1.1%, 6/544) patients met the strict definition of typical PM after re-evaluation. Patients with typical PM were MSA-negative (100% vs. 35.7%, p=0.003) and had CD8+ T cells surrounding or invading non-necrotic muscle fibres in muscle biopsies (100% vs. 7.8%, p<0.001) compared to the initially diagnosed PM patients. All typical PM patients achieved clinical remission at the second-year follow-up. Typical PM patients had a favourable prognosis compared to MSA-negative IMNM and unspecific myositis patients.
CONCLUSIONS:
Strictly defined typical PM is a rare clinical subtype in Chinese IIM patients. Typical PM patients with classical pathology were MSA-negative and responded well to treatment and had a favourable prognosis. It is crucial for clinicians to combine clinical, serological, and pathological features to properly distinguish PM from other IIM subtypes.
