Eosinophilic Pneumonias

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Description

  • Eosinophilic pneumonias (pulmonary eosinophilia) represent a heterogenous group of diseases with a similar clinical syndrome and overlapping findings on imaging.
  • Primary and secondary causes (1,2,3):
    • Primary:
      • Acute idiopathic eosinophilic pneumonia (AEP)
      • Chronic idiopathic eosinophilic pneumonia (CEP)
      • Eosinophilic granulomatosis with polyangiitis (EGPA) previously called Churg-Strauss syndrome (CSS) (4)
      • Simple pulmonary eosinophilia (SPE, i.e., Löffler syndrome) also overlaps pulmonary infiltrates with eosinophilia syndrome.
      • Hypereosinophilic syndromes (HES)
      • Eosinophilic bronchitis
    • Secondary causes: allergic bronchopulmonary aspergillosis (ABPA), parasitic infections, drug or toxin induced

Epidemiology

Incidence

  • Uncommon in United States, rates not specifically reported
  • CEP ~1–2% of all interstitial lung disease (ILD)

Prevalence

  • Predominant age: varies depending on exact process
  • Predominant sex:
    • AEP: male = female usually young patients
    • CEP: female > male (2:1), no difference after age 60 years
    • HES: male > female, 7:1 (3)
    • ABPA: 7–14% of all asthmatics, rare in nonasthmatics (5)

Etiology and Pathophysiology

  • No single etiology for the diverse cluster of diseases
  • Idiopathic (AEP, CEP)
  • Hypersensitivity (ABPA, Löffler syndrome)
  • Cigarette smoking (AEP)
  • Heavy dust and other occupational exposures (AEP)
  • Infectious: parasites, filariae, nematodes (Löffler syndrome), specifically Ascaris most common worldwide. Others include Strongyloides hookworms, filarial nematodes, Toxocara, and Paragonimus.
  • Drug induced: 120 known associations; most common: NSAIDs, minocycline, nitrofurantoin, cocaine

Genetics
No known genetic pattern

Risk Factors

  • Often idiopathic
  • AEP
    • Drugs
    • Inhalation of toxic products
    • Cigarette smoking
  • CEP
    • Drugs
    • Irradiation for breast cancer
    • Asthma
  • ABPA (3,5)
    • Asthma (usual duration 8 to 12 years prior)
    • Cystic fibrosis

Commonly Associated Conditions

  • Asthma (ABPA, EGPA)
  • Cystic fibrosis (ABPA)
  • Atopy (notable for CEP)
  • Tobacco use (AEP)

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