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Antisynthetase Syndrome (ASyS) ? Lung Findings
Etymology:
Named for the presence of autoantibodies targeting aminoacyl-tRNA synthetases, commonly affecting the lungs.
AKA:
- ASyS-related Interstitial Lung Disease (ILD).
What is it?
A form of autoimmune interstitial lung disease associated with antisynthetase syndrome, characterized by inflammation and fibrosis of lung parenchyma.
Caused by:
Autoimmune attack triggered by anti-aminoacyl-tRNA synthetase antibodies, leading to lung inflammation and fibrotic changes.
Most common:
- Lower lobe predominant NSIP (nonspecific interstitial pneumonia) pattern.
Based on Categories
Inflammation/Immune:
- Chronic inflammatory response in lung interstitium.
Idiopathic:
- Specific triggers for lung involvement remain unknown.
Resulting in:
- Chronic interstitial inflammation, fibrosis, and progressive respiratory dysfunction.
Structural Changes:
Parts:
- Predominantly affects the lower lung zones.
Size:
- Thickening of alveolar walls and interlobular septa.
Shape:
- Fibrotic reticulation and honeycombing in advanced stages.
Position:
- Diffuse but preferentially involves the lower lobes.
Character:
- Ground-glass opacities, reticulation, and traction bronchiectasis.
Time:
- Chronic, progressive course; acute exacerbations possible.
Pathophysiology:
Autoimmune activation leads to chronic alveolitis and progressive fibrosis, impairing gas exchange and lung compliance.
Diagnosis:
Clinical:
- Dyspnea on exertion, non-productive cough, and reduced exercise tolerance.
Radiology:
X-Ray:
Findings:
- Reticulonodular opacities in the lower zones.
Associated Findings:
- Volume loss in the lower lungs.
CT:
Findings:
- Ground-glass opacities, reticulation, traction bronchiectasis, and possible honeycombing (advanced stages).
- NSIP or OP patterns, predominantly in lower lobes.
Associated Findings:
- Subpleural sparing in NSIP.
Other Relevant Imaging Modalities:
- PET CT: May show increased metabolic activity in inflamed areas.
Other Diagnostic Procedures:
- Lung biopsy (if needed): Confirms NSIP or OP histology.
Differential Diagnosis
Most common:
- Idiopathic pulmonary fibrosis (IPF).
- Connective tissue disease-related ILD (e.g., systemic sclerosis).
Categories:
Inflammation/Immune:
- Rheumatoid arthritis-related ILD.
Idiopathic:
- NSIP without identifiable cause.
Recommendations:
- Early diagnosis with high-resolution CT.
- Monitor lung function and consider immunosuppressive therapy.
Key Points and Pearls:
- Lung involvement is the most critical prognostic factor in ASyS.
- NSIP pattern with lower lobe predominance is highly suggestive.
- Early treatment with immunosuppressants improves outcomes.