Examining Causes and Clinical Course of Exogenous Lipoid Pneumonia

Sick woman lying in bed
In many patients with exogenous lipoid pneumonia, respiratory symptoms and radiologic abnormalities continue to worsen even if the culprit exposure is identified and discontinued.

In many patients with exogenous lipoid pneumonia (ELP), respiratory symptoms and radiologic abnormalities continue to worsen even if the culprit exposure is identified and discontinued, according to study results published in CHEST.

The diagnosis of ELP is often difficult because findings may be nonspecific, and as a result, the clinical course of ELP has not been well-characterized. Therefore, researchers sought to determine the presenting clinico-radiologic features of ELP, its causative agents, and clinical course by searching the Mayo Clinic electronic medical records for patients diagnosed with ELP between 1998 and 2020.

Inclusion diagnostic criteria were as follows: lipoid pneumonia on histopathology, lipid-laden macrophages in bronchoalveolar lavage fluid, or fatty-attenuation of parenchymal opacities on chest computed tomography (CT). Additionally, all patients were required to have a clinician diagnosis of lipoid pneumonia in the absence of conditions known to cause endogenous lipoid pneumonia.

A total of 34 patients with a mean age of 71, one-half of whom were asymptomatic, were included. The diagnosis was confirmed by lung biopsy in 71%, by CT in 24%, and by bronchoalveolar lavage 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 cases, 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 while 50% worsened. Over a median follow-up interval of 1 year, CT abnormalities improved or resolved in 33% and progressed in 39%. Patients who deteriorated were older with a higher prevalence of gastrointestinal disorders than those who remained stable or improved.

“ELP is often asymptomatic and may not manifest fatty-attenuation on chest CT,” the study authors wrote. “Clinical and radiologic abnormalities persist or worsen in the majority of affected patients, even when the causative agent is discontinued.”


Samhouri BF, Tandon YK, Hartman TE, et al. Presenting clinico-radiologic features, causes, and clinical course of exogenous lipoid pneumonia in adults. CHEST. Published online February 26, 2021.doi:10.1016/j.chest.2021.02.037