IgG4-related lung disease IgG4-RLD

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.

  1. 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.
  2. 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.
  1. Lung nodules or masses:
    • Often bilateral and multiple.
    • May range in size and typically have irregular or lobulated margins.
  2. Bronchovascular bundle thickening:
    • Thickening along the bronchovascular structures, often seen as peribronchial cuffing.
  3. Ground-glass opacities:
    • Can be diffuse or patchy, representing areas of active inflammation.
  4. Interlobular septal thickening:
    • Thickened septa due to fibrosis, often associated with ground-glass opacities.
  5. Consolidation:
    • Areas of dense, homogeneous opacification, often subpleural or peribronchial.
  6. Pleural thickening or effusions:
    • Mild pleural thickening or small effusions may be present.
  7. Airway involvement:
    • In some cases, bronchiectasis or bronchial wall thickening can occur, especially if there is airway-centered inflammation.
  8. 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.

A chest CT scan showing findings typical of IgG4-related lung disease. The scan reveals multiple bilateral lung nodules with irregular margins, areas of ground-glass opacities, interlobular septal thickening, and areas of consolidation, particularly in the subpleural regions. Some bronchovascular bundle thickening is visible along with mild pleural thickening and small pleural effusions. There is also mediastinal lymphadenopathy visible near the center of the image, indicating systemic involvement.