Respiratory Bronchiolitis Interstitial Lung Disease (RB-ILD)

(aka Smoker’s Bronchiolitis)

Epidemiology

  • Some cases have been reported in collagen vascular diseases and mineral dust exposure
  • Time course: symptoms usually present for average of 37 months before presentation (typically, this is a longer course than for BOOP)
  • Mean Age of Onset: 40’s
  • Relationship to Smoking: almost all cases are smoking-related

Physiology

  • Accumulation of pigmented alveolar macrophages in respiratory bronchioles and adjacent alveoli
  • May represent a precursor to chronic lung disease in heavy smokers

Pathology

  • Tan-brown pigmented macrophages (“smoker’s macrophages”) within respiratory bronchioles, alveolar ducts, and alveoli/ mildly thickened brinchiole wall with ectasia (with mucous stasis)/ extension of metaplastic bronchiolar epithelium into nearby alveoli
  • Distant uninvolved parenchyma is normal or may demonstrate mild hyperinflation
  • Initial cases reported were probably misclassified as DIP (due to DIP-like appearance)

Diagnosis

  • ABG: mild hypoxemia
  • PFT’s: usually mild-moderate restriction with normal-slightly decreased DLCO (normal PFT’s in some cases)
    • Mixed obstructive/restrictive pattern: common
    • Isolated increased RV: occasionally seen
  • CXR/Chest CT Patterns
    • Diffuse fine reticulonodular infiltrates: with normal lung volumes
    • Bronchial wall thickening/ prominence of peribronchovascular interstitium/ small regular and irregular opacities/ small peripheral ring shadows are dustinctive features

Clinical

(insidious onset)

  • Dyspnea:
  • Cough (common):
  • Rales: coarse, end-inspiratory
  • Wheezing: reported in some cases
  • Absence of clubbing

Treatment

  • Steroids: favorable response in most series (improved PFT’s and CXR)
  • Smoking cessation: leads to improvement in symptoms, PFT’s, and CXR

Prognosis

  • No deaths have been reported

References

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