Exogenous Lipoid Pneumonia: Importance of a Thorough History
Pitfalls In Prescribing
How to Minimize Drug Therapy Risks
Exogenous lipoid pneumonia is commonly caused by the chronic aspiration of mineral oil.1 This rare form of pneumonia may also result from the aspiration or inhalation of several other fatty substances (Table 1).1-6 In addition, lipoid pneumonia may be caused by the intravenous injection of olive oil.7
Mineral oil pneumonia was first described in the 1920s, and recent reports show that it continues to be a problem.8-13 While many clinicians may not be familiar with mineral oil pneumonia, it has been reported several times in the peer-reviewed literature, including the New England Journal of Medicine.14
After aspiration of lipid particles into the lungs, a chronic inflammatory reaction occurs, including interstitial involvement associated with alveolar lipid accumulation. Although exogenous lipoid pneumonia due to acute aspiration/inhalation of lipids has also been reported,13 our article focuses on chronic aspiration. Examples of risk factors for lipoid pneumonia are shown in Table 2.
Typical Clinical Presentation and Diagnosis
More than 50% of patients are asymp-tomatic, and routine chest radiographs reveal nonspecific abnormalities, prompting further diagnostic tests.13 Symptomatic patients most commonly present with chronic mild cough and dyspnea. Less common symptomatic presentations include chest pain, hemoptysis, weight loss, and intermittent fever, perhaps due to the inflammatory reaction to oil or secondary infection.15 Physical examination of the chest may reveal rhonchi, crackles, wheezes, and dullness to percussion; however, the findings may be normal.
It is crucial to conduct a detailed history that includes questions about the use of mineral oil and other lipids (see Table 1). Because most patients will not think it is relevant to mention that they use laxatives or put petroleum jelly in the nose or ears, extensive questioning is essential. Ask parents of small children whether they give their child oil-based laxatives. If so, ask if the child frequently objects vigorously to ingesting them or if gagging is observed.13
In addition to a history of ingestion of mineral oil or use of other lipids that may have been aspirated, the diagnosis of lipoid pneumonia is based on several factors.12,13,16,17 Marchiori and colleagues13 have reviewed the assessment of lipoid pneumonia in detail, and they have pointed out that high-resolution CT is the optimal imaging modality for diagnosis. Common CT findings are listed in Table 3.
Examination of sputum may reveal oil in macrophages. Bronchoalveolar lavage may also establish the diagnosis, including findings such as lipid-laden macrophages and extracellular oily droplets, which is a common nonspecific finding suggestive of chronic aspiration. Finally, needle aspiration biopsy may be used.13
Although uncommon, possible complications include the following:
•Superinfection by non-tuberculous mycobacteria or Nocardia organisms.
•Pulmonary fibrosis from repetitive aspiration.
•Hypercalcemia, which is thought to result from the production of calcitriol by inflammatory cells.13
The first and most important step in management is to stop exposure to the oil or other lipid substance that is causing the problem. Because there is no evidence-based optimal therapy to date, management of lipoid pneumonia is mainly supportive care. Supportive modalities such as respiratory therapy, oxygen therapy, and mechanical removal of intrapulmonary lipids may be considered.13 Although the use of systemic corticosteroids in this setting has been reported, no studies have demonstrated efficacy. For some patients, discontinuation of the offending agent may result in slow resolution of symptoms and abnormal chest radiographs over a period of months.n
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