IgG4-related lung disease (IgG4-RLD) is part of the broader spectrum of IgG4-related disease (IgG4-RD), characterized by chronic inflammation and fibrosis in various organs. On chest CT, the imaging findings for IgG4-related lung disease can be diverse, depending on the specific pattern of involvement, but common features include:
Buzz words
Tendency to form masses
tissue destruction and fibrosis
Laboratory levels of IgG4 greater than 135 mg/dL
Anatomically
In IgG4-related lung disease (IgG4-RLD), involvement can occur in both the upper and lower lung fields; however, there are some patterns in presentation.
- Lower Lung Fields: Many cases tend to show more significant findings in the lower lung zones, including ground-glass opacities, nodules, and bronchial wall thickening.
- Upper Lung Fields: Some patients may exhibit lesions in the upper lung fields, including cysts or nodules, especially when there is a more extensive or chronic involvement.
- Bronchi: IgG4-related disease can cause bronchial thickening and narrowing due to peribronchial infiltration of IgG4-positive plasma cells and lymphocytes, often leading to symptoms like cough and wheezing.
- Lung parenchyma: The lung tissue itself can be affected, leading to interstitial pneumonia or nodules. This may present as areas of ground-glass opacities or consolidations on imaging.
- Lymph nodes: Mediastinal and hilar lymphadenopathy is frequently seen, often associated with other organ involvement.
- Pleura: Thickening of the pleura can occur due to the infiltration of IgG4-related plasma cells.
- Vasculature: There may be involvement of pulmonary vessels, leading to conditions such as pulmonary artery occlusion or vasculitis.
- Lung nodules or masses:
- Often bilateral and multiple.
- May range in size and typically have irregular or lobulated margins.
- Bronchovascular bundle thickening:
- Thickening along the bronchovascular structures, often seen as peribronchial cuffing.
- Ground-glass opacities:
- Can be diffuse or patchy, representing areas of active inflammation.
- Interlobular septal thickening:
- Thickened septa due to fibrosis, often associated with ground-glass opacities.
- Consolidation:
- Areas of dense, homogeneous opacification, often subpleural or peribronchial.
- Pleural thickening or effusions:
- Mild pleural thickening or small effusions may be present.
- Airway involvement:
- In some cases, bronchiectasis or bronchial wall thickening can occur, especially if there is airway-centered inflammation.
- Lymphadenopathy:
- Enlarged mediastinal or hilar lymph nodes may be seen, reflecting systemic involvement.
These findings, along with elevated serum IgG4 levels and histopathological features like dense lymphoplasmacytic infiltrates rich in IgG4-positive plasma cells, help establish the diagnosis of IgG4-related lung disease.