Polymyositis is a rare and favourable outcome subtype of idiopathic inflammatory myopathy in Chinese patients
Authors' conclusion
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.
Study context
- Population
- Chinese patients with idiopathic inflammatory myopathy (IIM) (2017 EULAR/ACR criteria) with muscle biopsyIIM patients with muscle biopsy
- Participants
- 544 patients
- Exposure
- Typical polymyositis (PM) vs initially diagnosed PM
- Typical PMn = 6
- Initial PMn = 129reference
- Outcome
- Prevalence of typical PM among IIM patients
Methodological detailsre-evaluation of serological and pathological data
- Re-evaluation of serological and pathological data
Main finding
As reported in the abstract
Prevalence of strictly defined typical PM
Typical PM
1.1%
6
Observational data: associations, not effects.
Further findings
MSA-negative
P = 0.003
CD8+ T cells surrounding or invading non-necrotic muscle fibres on biopsy
P < 0.001
Clinical remission · second-year follow-up
- All typical PM patients achieved clinical remission
Prognosis vs myositis-specific antibodies (MSA)-negative immune-mediated necrotising myopathies (IMNM) and unspecific myositis
- Typical PM had a favourable prognosis compared with MSA-negative IMNM and unspecific myositis
Original publication
Polymyositis is a rare and favourable outcome subtype of idiopathic inflammatory myopathy in Chinese patients. Clin Exp Rheumatol. Published 14 March 2024. doi:10.
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