• 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.