Legionnaire's pneumonia: Is there really an interstitial disease?

ObjectiveLegionella pneumonia is usually classified as “atypical pneumonia”, which suggests a predominance of interstitial patterns in chest X-rays. Based on a selection of recent clinical cases and a brief review of the literature, the aim of the study is to clarify, how far the actual radiological findings would be consistent with these expectations.Patients and methodsA retrospective analysis of 18 epidemic personal cases and a review of the literature data were performed to describe the chest X-ray findings of Legionella pneumophila (LP) community acquired pneumonia.X-ray review was performed simultaneously and in consensus by two radiologists (J.P.T., E.C.) and a physician (C.G.).ResultsFrom our series, 17 patients had an abnormal chest X-ray on admission. Among these pathological X-ray cases, infiltrates were more often confluent (n = 16), or patchy (n = 7), rather than interstitial (n = 1). Fifteen patients had infiltrates involving the lower lung fields. Bilateral distribution of abnormalities and pleural effusion were each observed in three cases. Radiological findings deteriorated between the second and seventh days following admission, particularly in the form of patchy infiltrates with pleural effusion.The review of the literature is consistent with these findings, by reporting prevalent confluent or patchy infiltrates.ConclusionsThese findings are consistent with the physiopathological particularity of this affection and incite us to avoid the classification “atypical pneumonia” in radiologic terminology. This term is more appropriate for clinical and microbiological use.