Lipoid pneumonia is also called pneumonitis and it results from the aspiration of lipids, and is linked to the use of mineral oil as a laxative. Lipoid pneumonia remains relatively unfamiliar to clinicians and the disease probably goes under diagnosed. This purpose of this article is to increase physicians’ awareness of lipoid pneumonia, its diagnosis and prevention.
Recent study was conducted on two illustrative cases of Lipoid pneumonia are reviewed. In an internal medicine ward, two cases of lipoid pneumonia were diagnosed within half a year. The patients were elderly and the lipoid pneumonia was associated with the use of mineral oil as a laxative agent. The computerized tomography that was conducted revealed bilateral low attenuation infiltrates, associated with a “crazy paving” pattern in one case. Both the cases were diagnosed by using Sudan Black staining procedure-in one on a transbronchial biopsy specimen, and in the other on sputum cytologic examination. Both the patients were suffering from neurologic diseases, and both were at risk of aspiration.
The clinical symptoms and signs, in both cases, continued for several months prior to diagnosis but once the use of mineral oil was discontinued, the signs and symptoms subsided. Therefore, it was concluded that elderly patients who are at risk of aspiration are susceptible to lipoid pneumonia and the condition may be under diagnosed. In most cases, mineral oil cathartics are the causative agent, therefore, an effort at primary prevention is recommended. It is suggested that the license of mineral oil for internal use can be reviewed or changed.
Exogenous lipoid pneumonia is referred to lung lesions that develop post aspiration or inhalation of animal, mineral oils or vegetable. Spickard and Hirschmann have made a reference of the circumstances under which aspiration of lipoid material occurs. The lipoid material smoothly glides down the respiratory tract, does not stimulate cough, and is not removed effectively by the cilia. Animal fats that can easily hydrolyze to fatty acids can cause more inflammation than vegetable or mineral oils. However, all types are successful in stimulating chronic granulomatous inflammation that is located in the lower or middle lobes.
Exogenous lipoid pneumonia is a condition that results from aspirating or inhaling fat-like material, such as mineral oil found in laxatives and various aerosolized industrial materials and it’s occurrence is uncommon. These substances bring out a foreign body reaction, and propagate fibrosis in the lung. Symptoms are absent or nonspecific and therefore, roentgenographic findings simulate other diseases. Hence, exogenous lipoid pneumonia is often unrecognized. However, accurate historical inquiries and simple laboratory tests can help to diagnosis correctly, eradicating the offending agent, and, thus improving the lung function before serious complications develop.
Although it is a rare form of non resolving pulmonary infiltrate, exogenous lipoid pneumonia is a great mimicker. It is often mistaken for bacterial pneumonia or cancer. Many cases are diagnosed by open lung biopsy or other invasive procedures. Depending on the degree of inflammation that occurs or the type of lipid ingested, the extent of the damage to the lung varies. The damage can fulminate to necrosis and hemorrhage. Symptoms may vary and range from none to respiratory failure. In one of the cases that were studied, the patient was ingesting Vaseline Intensive Care Lotion and baby oil as laxatives. This information was confirmed only after diagnosis was made by open lung biopsy.
Exogenous lipoid pneumonia
Most patients with exogenous lipoid pneumonia are elderly, usually in the late sixth or seventh decade of life. However, infants and mentally retarded persons are also prone to this condition. The factors that predispose a person to contracting this disease are an impaired swallowing mechanism caused by neurological and esophageal disorders, and the consistent use of the various kinds of oils – mineral, animal, and less commonly, the vegetable oils found in laxatives, nasal drops, mouth spray, oral lubricants, insecticides or traditional folk remedies. Lipid pneumonia also happens to be an occupational fire hazard of fire eaters. The irritation causing agent enters the lungs through aspiration, inhalation or during procedures which involve the use of iodized vegetable oils used as a radiopaque medium, such as lymphangiography, bronchography, hysterosalpingography, myelography or uterography.
Even though vegetable oils are mostly expectorated, residual elements often get blended in and can lead to exogenous lipoid pneumonia. Composed of liquid petroleum or paraffin, mineral oil is a mixture of long chain saturated hydrocarbons. It irritates the lung tissue and causes a diffuse parenchymal reaction or the development of localized masses called paraffinomas. Of all these substances animal fats are the most harmful to lung tissue. This is so because they are hydrolyzed by lipase in the pulmonary cells and broken down into free fatty acids, which could cause a severe inflammatory reaction and tissue necrosis. This process has been observed in infants and children with exogenous lipoid pneumonia to be a result of force feeding of animal fat (ghee), a cultural practice in Saudi Arabia.
When oil enters the lung, there are 3stages in the pathologic process that leads to the development of exogenous lipoid pneumonia. The first stage consists of a toxic agitation of capillary endothelium with plasma exuding into the alveoli. In the next stage, alveolar and interstitial macrophages get activated then phagocytose and degrade the oil.In the final stage, fibrointerstitial and granulomatous reactions develop. Depending on the quality and quantity of oil present, these stages vary in severity. With the inhalation of animal fat, the high lipid content represses phagocytosis, leaving the pulmonary lymphocytes as the main cells responsible for the removal of the inhaled fat. In such cases, fat-laden macrophages and prominent pleural lymphocytes can be observed on histologic examination and which could easily lead to the mistaken diagnosis of lymphatic carcinomatosis.
Endogenous lipoid pneumonia
Also called cholesterol pneumonitis, endogenous lipoid pneumonia is caused by the collection of intrinsic lipids in the lungs. It is generally observed in persons with chronic bronchial obstruction similar to tumors or foreign bodies. Other risk factors include fat embolism, pulmonary alveolar proteinosis, lipid storage diseases such as Gaucher’s disease and Niemann-Pick disease and disseminated lipogranulomatosis.
Endogenous lipoid pneumonia has also been observed in patients with Hodgkins disease. A 5 year old child with a serious neurodevelopmental disorder reportedly developed a combination of endogenous and exogenous lipoid pneumonia and pulmonary alveolar proteinosis. Endogenous lipoid pneumonia has also been linked to lung cancer. In one research conducted, endogenous lipoid pneumonia was diagnosed in the resected lungs of 33 of 147 patients with lung cancer. It was found in 16 out of 89 (18%) of patients with adenocarcinoma and in 17 of 55 (31%) patients with squamous cell carcinoma. In 23 cases, it was observed that endogenous lipoid pneumonia was localized to lung parenchyma distal to the airway obstructed by the tumor, and of these 16 were patients with squamous cell carcinoma. Out of 5 patients with adenocarcinoma, 4 had endogenous lipoid pneumonia present distal to the tumor and having spread to isolated segments. These results indicate that transbronchial dissemination of the breakdown products of adenocarcinoma cells, including mucin, could contribute to the spread of the nonobstructive component of endogenous lipoid pneumonia.
A histopathologic examination of lung tissue of patients with non–small cell lung cancer has revealed changes similar to those observed in endogenous lipoid pneumonia, along with pulmonary alveolar proteinosis, located near the non–small cell lung cancer. One study described coexisting changes similar to those seen in endogenous lipoid pneumonia in the vicinity of primary lung tumors, particularly in samples of tissue from patients with squamous cell and large cell carcinoma.
When normal lung tissue is chemically analysed, it shows a total fat content of 8.63 per 100 g of dry tissue, of which 19% is cholesterol; although this percentage shows a marked increase in smokers. When the breakdown of these cells takes place, it results in the lipid gaining access to lung parenchyma and it is phagocytosed by the pulmonary macrophages. The absence of lysosomes in these macrophages impairs their ability to resist bacterial infections, and renders the patient more susceptible to opportunistic infections.If the macrophage nucleus displays morphologic evidence of an extreme increase in activity— parachromatic clearing, chromatin clumping and hyperchromatic prominent nucleoli – a diagnosis of lung carcinoma is possible.
Some patients can remain asymptomatic. Whereas in some patients, symptoms and signs of the underlying diseases or complications may be evidently present. Physical findings through physical examinations vary from normal to those of chronic lung diseases.
The diagnosis of exogenous lipoid pneumonia is suggested by a history of oil aspiration or inhalation, along with radiographic findings.
There is no typical radiographic picture indicative of lipoid pneumonia. Initial chest radiographs may reveal an alveolar mottling resulting from the collection of lipid in the alveolar spaces. Subsequently, interstitial images form because of the migration of macrophages and thickening of alveolar septae with fibrosis. Sometimes a localized nodule(parafinoma) may be visible in chest radiographs which could easily be confused with many implications – neoplasm or tuberculosis; asynchronous bilateral infiltrates or bilateral cavitary lesions; cavitary lesions that are quite similar to Wegener’s granulomatosis; In a demonstrative study consisting of 44 patients suffering from exogenous lipoid pneumonia, the most common radiographic observations were alveolar nodules and alveolar consolidation, ground-glass opacities. These features were found to be bilateral, hypodense and mainly prevalent in the lower and posterior zones of the lobes but the sub pleural lobes were spared.
Another report identified bilateral air space consolidation, consisting of mass like lesions and a reticulonodular pattern as the major radiographic observations. A analysis of chest x-rays of 24 children who developed lipoid pneumonia due to the aspiration of animal fat revealed multilobar consolidation. Five of the children had right perihilar infiltrates, another 5 had bilateral perihilar infiltrates with or without associated lobar consolidation and two of them had bilateral perihilar infiltrates with or without associated lobar consolidation.
Due to the low diagnostic accuracy of chest x-rays, computed tomography (CT) scanning is considered the optimal method for establishing diagnosis of endogenous lipoid pneumonia. A CT scan of the chest reveals low-density consolidation with negative attenuation values, indicating the presence of fat. The scans may also show diffuse parenchymal consolidation and fat with localized areas of consolidation and subpleural pulmonary fibrosis. In scans showing diffuse consolidation, the attenuation is decreased but is higher than that of subcutaneous fat.
Pulmonary consolidation with fatty changes, areas of ground-glass opacities, unspecific but low attenuation values, septal lines, and centrilobular interstitial thickening have been revealed in high resolution CT scanning. The CT image of ground-glass attenuation is visible. Out of 7 patients with exogenous lipoid pneumonia, a “crazy-paving pattern” (ground-glass attenuation with superimposed septal thickening) was observed on high resolution CT in 5 of them, either in isolation or all around the pulmonary consolidation. In 2 cases cystic and traction bronchiectasis changes consistent with fibrosis were seen.
Magnetic resonance imaging (MRI) has revealed pulmonary consolidation of a high intensity on T1-weighted images consistent with lipid content. Results on lipid sensitive (chemical-shift) MRI include a loss of signal intensity in an area of airspace disease that was considered typical for the presence of lipid.
A conclusive diagnosis can be made by analyzing bronchoalveolar lavage (BAL) fluid or samples obtained via transbronchial biopsy. The BAL fluid may appear normal, milky, or hemorrhagic; further examination may reveal lipid-laden macrophages, a few activated lymphocytes and many eosinophils. One demonstrative study of BAL examination of specimens from 39 patients with exogenous lipoid pneumonia revealed that 14% had a neutrophilic alveolitis, 23% had a lymphocytic alveolitis and 31% had mixed alveolitis (lymphocytic and neutrophilic).
The cytologic manifestation of lipid-laden macrophages in the BAL specimen is consistent with, but not specific for, lipoid pneumonia. Such macrophages can be seen in many other disorders. The lipid-laden macrophage index may be useful for diagnosis. This is a technique for quantification in which the amount of lipids in each cell is graded from 0 to 4 in 100 consecutive alveolar macrophages. The grades are then assessed wherein a score of 100 or greater indicates aspiration lipoid pneumonia. However this index cannot differentiate between endogenous and exogenous forms of lipoid pneumonia in adults.
Subsequent research rendered obsolete the use of the lipid-laden macrophage index as confirmation of aspiration pneumonia in infants since there were many index values greater than 100 in the tracheal aspirate specimens from infants who had not received lipids intravenously as well as from those who had received the infusions.
CT-guided needle biopsy or thoracotomy or Transbronchial biopsy may be required to confirm the diagnosis of lipoid pneumonia and to negate the possibility of primary or metastatic tumors in the lung. Some other serious conditions in the differential diagnosis consist of pulmonary alveolar proteinosis, pulmonary hemosiderosis, eosinophilic pneumonia, bronchial carcinoid, pulmonary hemosiderosis and hamartomas.
Lipid pneumonia is treated with antibiotics, corticosteroids and also with intravenous immunoglobulins.