Lipoid Pneumonia

(aka Exogenous Lipoid Pneumonia)

Types of Oil

  • Mineral Oils (most commonly aspirated oils) -> oil droplets are taken up by macrophages, macrohages disintegrate and release the oil droplets, which inhibit ciliary activity (therefore, oil is not expectorated and cycle continues) -> leads to development of fibrotic or granulomatous reaction
  • Neutral Oils: vegetable oils -> do not elicit a local reaction and are removed by expectoration
    • Olive Oil
    • Castor Oil
  • Animal Fats: rapidly hydrolyzed -> liberated fatty acids produce tissue necrosis and subsequent fibrosis
    • Milk
    • Butter

Etiology of Exogenous Lipoid Pneumonia

  • Nocturnal Aspiration of Mineral Oil: usually in older patients as a treatment for constipation
    • Mineral oil is a mix of inert long-chain saturated hydrocarbons (obtained from petroleum)
    • Mineral oil inhibits the cough reflex and ciliary motility, facilitating inhalation
  • Aspiration of Petroleum Gels
    • Vicks Vapo-Rub: used for dry nasal passages
    • Petroleum Gel Used to Lubricate ET Tube: during intubation
  • Aspiration of Other Oils
    • Oily nose drops
    • Olive oil
    • Milk
    • Cod liver oil
    • Paraffin oil
    • Poppy seed oil
    • Methenamine mandelate suspension (urinary antiseptic)
  • Aspiration of Oil-Based Sprays

    • Motor oil sprays
    • Industrial oil sprays
  • Cyclosporin A (CSA):

  • Iodine/Radiographic Contrast:

Physiology

  • Aspiration of exogenous lipid (oily nosedrops/mineral oil/etc) into lungs
  • Underlying GERD is an important contributing factor

Clinical Presentations

  • Asymptomatic
  • Lung Nodule
    • Diagnosis
      • CXR/Chest CT: solitary lung nodule
  • Alveolar or Interstitial Pneumonia (see [[Pneumonia]] and [[ILD-Etiology]])
    • Diagnosis
      • CXR/Chest CT
        • Alveolar infiltrates: especially in the lower lobes
        • ”CT Angiogram Sign”: branching pulmonary arteries seen within consolidated lung on Chest CT -> however, this sign is not specific for lipoid pneumonia
        • HRCT: “Crazy Paving” -> ground glass density in a mesh-work of reticular lines representing thickened intralobular septa (this pattern is typical for alveolar proteinosis, but has also been reported with lipoid pneumonia and other conditions)
      • FOB:
        • BAL: before fixation, stained with oil-red-O or Sudan red will show alveolar macrophages with vacuolated cytoplasm (this strongly suggest the diagnosis in the proper clinical setting)
        • TBB: characteristic circular empty spaces in tissue sections (due to loss of lipid during prep) with surrounding inflammation
      • OLB: vacuolated intra-alveolar macrophages
        • Foreign-body granulomas with giant cells
        • Chronic: granulomatous pneumonitis with fibroblastic proliferation, fibrosis, masses of foamy macrophages, foreign-body giant cells
  • Acute Lung Injury-ARDS (see [[Acute Lung Injury-ARDS]])
    • Epidemiology: may occur

Treatment

  • Withdraw Agent
    • 46% of cases improve
    • 25% stabilize
    • 21% continue to deteriorate (due to fibrosis and respiratory failure)
  • Corticosteroids: effective in acute and subacute cases
    • May be effective in a few chronic cases
  • Whole Lung Lavage: has been used in some cases

References

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