Lipoid pneumonia results from the aspiration of oil and can also be caused, in rare cases, by the injection of oil into the skin, with lymphatic transport to the lungs.

 It can look like acute or chronic pneumonia or a localized granuloma (called paraffinoma). 

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Among the types of oil that are aspirated, animal oil causes more sclerosis than vegetable oil, which in turn causes more sclerosis than mineral oil. Aspirated milk causes a special form of lipoid pneumonia.

Aspiration of lipid gastric contents or of oil given as medication can result in exogenous lipoid pneumonia, which in turn becomes super-infected with mycobacteria. Recognition of the distinctive histology permits the diagnosis of this complication.

The effects of aspiration are dependent on the material so that a diverse pattern of involvement may be seen:

Gastric acid - pulmonary edema , haemorrhage and alveolar damage leading to Mendelssohn’s syndrome.

Food - pneumonia, foreign body reactions and abscesses.

Lipid  - exogenous lipid pneumonia leading to interstitial fibrosis

       - paraffinoma , a localized form of the above.

Exogenous lipid pneumonia must be distinguished from the endogenous form which is a  component of the obstructive pneumonitis seen distal to an occluded bronchus. The most frequently documented cause of endogenous lipoid pneumonia is bronchial obstruction by tumour.  Hence the ‘golden’ pneumonia is seen near central tumours. The type of pneumonia, which has been referred to as golden pneumonia, results from the filling of alveoli with foamy macrophages that are packed with small lipid droplets and cellular detritus. Niemann-Pick disease should be considered for any patient with unexplained diffuse endogenous lipid pneumonia, even when disease is limited to the lungs and presentation is during adulthood.

The clinical presentation of exogenous lipid pneumonia  is nonspecific and ranges from the totally asymptomatic patient with incidental radiologic finding, to the patient with acute or chronic symptoms attributable to pneumonia, pulmonary fibrosis, or cor pulmonale.

 Endogenous Causes of Pneumonia characterized by Lipid Accumulation.:click here (NEJM)

Exogenous Causes of Pneumonia Characterized by Lipid Accumulation.:click here (NEJM)

Careful attention to the above, combined with an appropriate clinical history, is adequate for the diagnosis of most cases.

Bronchoscopy with bronchoalveolar lavage can be successful in establishing the diagnosis of exogenous lipid pneumonia by demonstration of a high lipid-laden macrophage index , but chemical  analysis or infra-red spectrophotometry will provide incontrovertible evidence.