Lipoid Pneumonia Complicating Megaesophagus Secondary to Chagas Disease: High-resolution Computed Tomography Findings

Presenting Clinicoradiologic Features, Causes, and Clinical Course of Exogenous Lipoid Pneumonia in Adults

BACKGROUND

Exogenous lipoid pneumonia (ELP) develops when lipid-containing substances enter the airways through aspiration or inhalation and incite an inflammatory response. The diagnosis of ELP often is difficult because findings may be nonspecific. The clinical course of ELP has not been well characterized.

RESEARCH QUESTION

What are the presenting clinicoradiologic features of ELP, its causative agents, and clinical course?

STUDY DESIGN AND METHODS

We searched the Mayo Clinic electronic medical records for patients diagnosed with ELP between 1998 and 2020. Inclusion diagnostic criteria were: (1) lipoid pneumonia (LP) on histopathologic examination, (2) lipid-laden macrophages in BAL fluid, or (3) fatty attenuation of parenchymal opacities on chest CT imaging. Additionally, all patients were required to have a clinician diagnosis of LP in the absence of conditions known to cause endogenous LP.

RESULTS

Thirty-four patients were identified. Mean age was 71 years, with no sex predominance; one-half were asymptomatic. The diagnosis was confirmed by lung biopsy (including three lobectomies for suspected malignancy) in 71% of patients, CT scan in 24% of patients, and BAL in 5% of patients. Most patients manifested bilateral parenchymal opacities that commonly involved the lower lobes; fatty attenuation was identifiable in only 41% of patients. A causative substance was identified in 79% of patients, in most cases after the diagnosis was established. Over a median follow-up of 1.2 years, only 20% of patients with chronic respiratory symptoms improved, whereas 50% worsened. Over a median follow-up interval of 1 year, CT scan abnormalities improved or resolved in 33% of patients and progressed in 39% of patients. Patients who deteriorated were older, with a higher prevalence of GI disorders than those who remained stable or improved.

INTERPRETATION

ELP often is asymptomatic and may not manifest fatty attenuation on chest CT imaging. Clinical and radiologic abnormalities persist or worsen in most affected patients, even when the causative agent is discontinued.

A case report of exogenous lipoid pneumonia associated with avocado/soybean unsaponifiables

BACKGROUND

Exogenous lipoid pneumonia is a rare disease resulting from intra-alveolar accumulation of lipids of mineral, vegetal, or animal origin, that induce a foreign body type of inflammatory reaction in the lungs. Gastroesophageal reflux disease and other esophageal abnormalities have often been associated with this disease.

CASE PRESENTATION

We herein report the case of an 83-year-old patient in whom a follow-up chest computed tomography scan, for a lingular consolidation, showed multifocal ground glass and consolidative opacities with areas of low attenuation, suggestive of exogenous lipid pneumonia. The patient had been on piascledine capsules (avocado/soybean unsaponifiables) for 20 years and had a hiatal hernia with documented gastroesophageal reflux disease. After thorough history taking, no other predisposing factors were found. The diagnosis was confirmed using oil red staining of bronchoalveolar lavage showing lipid-laden macrophages and extracellular lipid droplets.

CONCLUSIONS

To our knowledge, this is the first case of ELP secondary to avocado/soybean unsaponifiables in the literature.

Metabolic Functions of the Lung, Disorders and Associated Pathologies

The primary function of the lungs is gas exchange. Approximately 400 million years ago, the Earth's atmosphere gained enough oxygen in the gas phase for the animals that emerged from the sea to breathe air. The first lungs were merely primitive air sacs with a few vessels in the walls that served as accessory organs of gas exchange to supplement the gills. Eons later, as animals grew accustomed to a solely terrestrial life, the lungs became highly compartmentalized to provide the vast air-blood surface necessary for O2 uptake and CO2 elimination, and a respiratory control system was developed to regulate breathing in accordance with metabolic demands and other needs. With the evolution and phylogenetic development, lungs were taking a variety of other specialized functions to maintain homeostasis, which we will call the non-respiratory functions of the lung and that often, and by mistake, are believed to have little or no connection with the replacement gas. In this review, we focus on the metabolic functions of the lung, perhaps the least known, and mainly, in the lipid metabolism and blood-adult lung vascular endothelium interaction. When these functions are altered, respiratory disorders or diseases appear, which are discussed concisely, emphasizing how they impact the most important function of the lungs: external respiration.