• Etymology

  • Derived from the term bronchiolitis, indicating inflammation of the small airways, and interstitial lung disease (ILD), referring to a group of disorders affecting the lung interstitium. RB-ILD is named for its association with respiratory bronchiolitis and its progression into interstitial lung pathology.

  AKA

  • RB-ILD
  • Smoking-related interstitial lung disease

  What is it?

  • RB-ILD is a smoking-related interstitial lung disease characterized by inflammation and macrophage accumulation in the respiratory bronchioles and adjacent alveoli, progressing to interstitial changes in susceptible individuals. It is considered a clinical-pathologic entity distinct from simple respiratory bronchiolitis.

  Caused by:

  • Most common cause:
    • Cigarette smoking
  • Less common causes:
    • Inflammation:
      • Chronic exposure to secondhand smoke
    • Other:
      • Possible genetic predisposition in some individuals

  Resulting in:

  • Diffuse interstitial inflammation and fibrosis
  • Chronic cough and dyspnea
  • Reduced gas exchange

  Structural Changes:

  • Pigmented macrophage accumulation in respiratory bronchioles
  • Peribronchiolar and interstitial inflammation
  • Mild to moderate fibrosis in chronic cases

  Pathophysiology:

  • Chronic exposure to cigarette smoke leads to macrophage activation in the respiratory bronchioles, with subsequent inflammation and damage to surrounding alveoli and interstitial tissues. Persistent inflammation can result in interstitial fibrosis and impaired pulmonary function.

  Pathology:

  • Accumulation of pigmented macrophages (smoker’s macrophages) in bronchioles and alveoli
  • Interstitial thickening with lymphocytic infiltration
  • Mild fibrosis and alveolar wall remodeling

  Diagnosis

  Clinical:

  • Symptoms include:
    • Insidious onset of dyspnea
    • Persistent cough, often with sputum production
    • History of significant cigarette smoking
  • Physical examination:
    • Fine crackles on auscultation
    • Cyanosis or clubbing in advanced cases

  Radiology:

  • CXR:
    • Diffuse reticulonodular opacities
    • Often subtle and non-specific
  • CT of the Chest:
    • Centrilobular nodules
    • Ground-glass opacities
    • Peribronchiolar thickening
    • Mild interlobular septal thickening

  Labs:

  • Rarely diagnostic but may include:
    • ABG abnormalities in advanced disease
    • Autoimmune panel to exclude other ILDs

  Management:

  • Smoking cessation:
    • The cornerstone of management, often halting disease progression
  • Supportive care:
    • Supplemental oxygen in hypoxemic patients
    • Pulmonary rehabilitation for symptomatic improvement
  • Immunomodulation:
    • Corticosteroids in severe or progressive cases

  Radiology Detail

  CXR

  Findings:

  • Reticulonodular opacities, more prominent in the mid and upper lung zones
  • Hyperinflation in some cases due to coexisting emphysema

  Associated Findings:

  • Subtle peribronchiolar changes

  CT of the Chest

  Parts:

  • Respiratory bronchioles and adjacent alveoli

  Size:

  • Centrilobular nodules measuring 1-3 mm

  Shape:

  • Nodular, ground-glass, or patchy opacities

  Position:

  • Predominantly upper lobe involvement

  Character:

  • Peribronchiolar thickening with ground-glass attenuation

  Time:

  • Chronic, with potential stabilization after smoking cessation

  Associated Findings:

  • Coexisting emphysema in heavy smokers
  • Subtle fibrosis in advanced disease

  Other relevant Imaging Modalities

  MRI/PET CT/NM/US/Angio:

  • MRI: Rarely used but may demonstrate inflammatory changes
  • PET-CT: May show low-level metabolic activity in inflammatory areas

  Pulmonary Function Tests (PFTs):

  • Mild to moderate restrictive pattern
  • Decreased diffusion capacity (DLCO) in advanced disease

  Recommendations:

  • CT of the Chest is the imaging modality of choice for assessing RB-ILD
  • Encourage smoking cessation as a primary intervention
  • Monitor disease progression with serial pulmonary function tests and imaging

  Key Points and Pearls:

  • RB-ILD is a smoking-related interstitial lung disease distinct from simple respiratory bronchiolitis.
  • CT findings include centrilobular nodules and ground-glass opacities, with upper lobe predominance.
  • Smoking cessation is the most critical intervention and can prevent further disease progression.
  • Coexisting emphysema may complicate the clinical picture and management.

   

• • • 

Etiology Cigarette Smoke

Difference between RB , RB ILD and desquamative interstitial pneumonia (DIP) is that RB has centrilobular findings while RB ILD has centrilobular changes and ground glass changes and DIP has centrilobular findings ground glass changes and cysts.

 

• Histopathology characterized by
  • • pigmented macrophages and
    • respiratory bronchioles and alveoli
      • mild interstitial inflammatory
      • alveolar septa in the peribronchial may be mildly thickened
      • no significant fibrosis

DIP is similar to RB-ILD,

• •  DIP and  RB-ILD are a spectrum
  • differing in compartments involved
  • DIP not bronchiolocentric.
  • hyperplasia of the alveolar type II cells
  • distribution pattern more homogeneous a
  • mild peribronchial fibrosis

Buzz

Use your words

respiratory bronchiolitis = inflammation of the respiratory bronchioles.

dirty lung appearance

centrilobular lung nodules

ground glass

air trapping

emphysema

Respiratory Bronchiole

 

 

Secondary Lobule

Inhalation – Upper Lobes

centrilobular ground glass nodules

References and Links

Attili, A.K etal  Smoking-related Interstitial Lung Disease: Radiologic-Clinical-Pathologic Correlation RadioGraphics Vol. 28, No. 5Gupta et al Diffuse Cystic Lung Disease: Part I  American Journal of Respiratory and Critical Care Medicine 191(12)  April 2015Sieminska A, et al  Respiratory bronchiolitis-interstitial lung disease Orphanet Journal of Rare Diseases volume 9: 106 (2014)Wiki

• TCV

  Smoking Related Diseases Map

Lung Disease and Cigarette Smoking

Respiratory Bronchiolitis

Desquamative Interstitial Pneumonia

Pulmonary Langerhans Cell Histiocytosis

Emphysema

Airspace Enlargement and Fibrosis

Idiopathic Pulmonary Fibrosis

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