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Published on: February 8, 2019
Muscle-dominant ANCA-associated vasculitis: a single-center cohort study.
Akihiro Yahata1, Naoki Nakamoto1, Hiroshi Oiwa2
1Department of Rheumatology, Hiroshima City Hiroshima Citizens Hospital, 7-33 Motomachi, Naka-ku, Hiroshima City, Hiroshima, 730-8518, Japan.
Rheumatology International
|May 23, 2026
Summary
Muscle-dominant ANCA-associated vasculitis (AAV) presents uniquely with MPO-ANCA positivity, normal creatine kinase (CK) levels, and elevated rheumatoid factor (RF). This distinct pattern, potentially linked to interstitial lung disease (ILD), suggests a specific AAV subtype.
Area of Science:
- Rheumatology
- Immunology
- Internal Medicine
Background:
- ANCA-associated vasculitis (AAV) encompasses conditions like microscopic polyangiitis (MPA) and granulomatosis with polyangiitis (GPA).
- Muscle involvement in AAV can occur but is often overshadowed by other organ manifestations.
- Identifying distinct clinical patterns within AAV is crucial for accurate diagnosis and management.
Purpose of the Study:
- To define the clinical characteristics of muscle-dominant AAV in a single-center cohort.
- To compare muscle-dominant AAV patients with other AAV patients.
- To identify potential diagnostic markers and patterns associated with muscle-dominant AAV.
Main Methods:
- Retrospective analysis of consecutive patients newly diagnosed with MPA or GPA.
- Definition of muscle-dominant AAV excluding other major organ involvement.
- Comparison of clinical, serological (MPO-ANCA, RF, CK), and imaging (MRI, ILD prevalence) data between muscle-dominant AAV and other AAV patients.
Main Results:
- Eight percent of patients (8/72) were classified with muscle-dominant AAV.
- All muscle-dominant AAV patients were MPO-ANCA-positive with normal serum creatine kinase (CK) levels despite MRI-confirmed muscle inflammation.
- The muscle-dominant AAV group showed significantly higher rheumatoid factor (RF) levels and a trend towards increased interstitial lung disease (ILD) prevalence compared to controls.
Conclusions:
- Muscle-dominant AAV is characterized by MPO-ANCA positivity, elevated RF, normal CK levels, and MRI-proven muscle involvement.
- A potential clinical pattern, tentatively named IMARM (ILD, MPO-ANCA, RF, myopathy), is suggested.
- Further research is warranted to validate this distinct AAV phenotype and its implications.
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