Clinical and radiological manifestations of lipoid pneumonia according to etiology: Squalene, omega-3-acid ethyl esters, and idiopathic

Objectives: Clinical manifestations of lipoid pneumonia (LP) vary depending on the causative agents or underlying causes. The aim of the present study was to investigate the clinical and radiological features of LP, classified according to etiologic agents. Methods: The clinico-radiological characteristics of LP patients were retrospectively compared among groups: exogenous versus idiopathic and squalene versus omega-3-acid ethyl esters (O-3-AEE) versus idiopathic. Idiopathic group was defined as LP with no proven or reported etiological evidence. Results: Twenty-two patients met the diagnostic criteria for LP: squalene (9 [41%]), O-3-AEE (6 [27%]), olive oil (1 [5%]), and idiopathic (7 [32%]). Compared with the exogenous group, the idiopathic group showed a higher recurrence rate; higher frequencies of bronchial anthracofibrosis (BAF) and bronchoalveolar lavage (BAL) lymphocytosis; and a higher rate of crazy-paving pattern and lower rate of consolidation on computed tomography scan. In three-group tests, compared with the O-3-AEE group, the squalene group exhibited a significantly higher percentage of neutrophils and a higher rate of right middle lobe (RML) involvement. Conclusions: In comparison with the exogenous group, the idiopathic group demonstrated BAL lymphocytosis, higher rates of recurrence and BAF, and a higher rate of crazy-paving pattern. Compared with the O-3-AEE group, the squlaene group showed a higher percentage of BAL neutrophils and predominant RML involvement.