Myositis with ILD
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myositis AND "interstitial lung disease"
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myositis associated interstitial lung disease management guideline 2025
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https://pubmed.ncbi.nlm.nih.gov/40912974/
Myositis-associated interstitial lung disease (myositis-ILD)
Myositis-ILD is lung involvement caused by an idiopathic inflammatory myopathy, most often dermatomyositis, polymyositis, clinically amyopathic dermatomyositis, or anti-synthetase syndrome. It can appear before, with, or after muscle disease, and occasionally is the predominant manifestation.
Key phenotypes and antibodies
| Pattern | Typical clues | ILD risk/course |
|---|---|---|
| Anti-synthetase syndrome | Myositis, ILD, inflammatory arthritis, Raynaud phenomenon, fever, mechanic's hands | Common ILD; may be chronic or relapsing |
| Anti-MDA5 dermatomyositis | Often minimal muscle weakness, characteristic DM rash, ulcers, palmar papules | High risk of rapidly progressive ILD |
| Anti-Ro52 co-positivity | Often coexists with myositis-specific antibodies | Associated with more severe/progressive ILD in several cohorts |
| Anti-PM/Scl, Ku, U1-RNP | Overlap connective-tissue disease features | Variable ILD risk |
Anti-Jo-1 is the commonest anti-synthetase antibody. Anti-PL-7 and anti-PL-12 may present with prominent lung disease and little overt myositis. ILD may be the only initial manifestation of anti-synthetase syndrome.
Clinical presentation
- Exertional dyspnea, dry cough, reduced exercise tolerance
- Fine bibasal inspiratory crackles
- Hypoxemia, especially with exertion
- Muscle weakness, rash, arthritis, Raynaud phenomenon, or mechanic's hands may point to the underlying myositis
- Rapidly worsening dyspnea over days to weeks suggests rapidly progressive ILD and needs urgent specialist assessment, particularly in anti-MDA5 disease.
Evaluation
- HRCT chest: usually shows nonspecific interstitial pneumonia (NSIP), organizing pneumonia (OP), or mixed NSIP-OP patterns. UIP is less frequent.
- Pulmonary function tests: FVC, TLC, and DLCO at baseline, then serially.
- Oxygenation: resting and exertional saturation, often a 6-minute walk test.
- Myositis assessment: CK, aldolase, liver enzymes, muscle strength, skin examination, MRI or biopsy where appropriate.
- Antibodies: myositis-specific and myositis-associated antibody panel, including anti-synthetase antibodies, MDA5, TIF1-gamma, Mi-2, SRP, HMGCR, Ro52, PM/Scl, and Ku.
- Exclude mimics or complications: infection, drug toxicity, aspiration, pulmonary edema, pulmonary embolism, and malignancy where indicated.
Multidisciplinary review involving rheumatology, pulmonology, radiology, and sometimes pathology is preferred.
Treatment principles
Treatment is individualized by severity, rate of progression, infection risk, antibody phenotype, and extrapulmonary disease.
- Clinically significant/progressive ILD: glucocorticoids are commonly used initially, generally alongside a steroid-sparing immunosuppressant rather than as prolonged monotherapy.
- Common steroid-sparing options: mycophenolate mofetil, azathioprine, tacrolimus or cyclosporine.
- More severe, refractory, or rapidly progressive disease: rituximab and cyclophosphamide are commonly considered; IVIG may help selected patients, especially where muscle, dysphagia, infection risk, or refractory disease complicate management.
- Anti-MDA5 rapidly progressive ILD: often requires early aggressive combination immunosuppression under specialist care. Delaying treatment can be dangerous.
- Progressive fibrosing ILD despite immune control: antifibrotic therapy may be considered in selected patients by an ILD specialist.
- Supportive care includes pulmonary rehabilitation, oxygen when indicated, smoking cessation, vaccination planning, reflux/aspiration management, bone protection, and prophylaxis against opportunistic infection when immunosuppression is substantial.
A rheumatology text notes use of mycophenolate and calcineurin inhibitors for myositis-ILD, with cyclophosphamide, rituximab, IVIG, and pulse methylprednisolone reserved in more serious contexts (Firestein & Kelley's Textbook of Rheumatology, 2-Volume Set).
Monitoring
- Symptoms, oxygen requirement, and examination at each review
- PFTs roughly every 3-6 months during active disease, then individualized
- Repeat HRCT when symptoms or PFTs worsen, or to clarify treatment response
- Monitor muscle, skin, joints, swallowing, medication toxicity, infections, and malignancy risk according to myositis subtype
Current CTD-ILD guidance includes idiopathic inflammatory myopathies and emphasizes structured screening, diagnosis, monitoring, and treatment algorithms, though evidence certainty remains limited for some decisions, as summarized in the 2025 ERS/EULAR guideline.
Prognosis
Outcome ranges from stable, treatment-responsive disease to severe progressive fibrosis. Worse prognosis is associated with rapidly progressive ILD, marked hypoxemia, declining FVC/DLCO, extensive HRCT involvement, and anti-MDA5 phenotype. Anti-synthetase ILD may relapse and needs long-term follow-up.
A recent systematic review of anti-synthetase ILD supports the importance of early recognition and sustained monitoring, but treatment evidence is mostly observational rather than from large randomized trials.
Seek urgent medical care for rapidly increasing breathlessness, oxygen saturation below usual baseline, chest pain, fever while immunosuppressed, confusion, or inability to speak full sentences due to breathlessness.
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