Legionella pneumonia presenting with reverse halo sign

A case of a previously healthy man with community-acquired pneumonia who progressed to acute respiratory distress syndrome, with reverse halo sign (RHS) on chest computed tomography, is reported. A urinary Legionella antigen test was positive for Legionella pneumophila . The typical radiographic features of Legionella pneumonia are bilateral or unilateral, single or multifocal airspace opacifications (most common), and/or ground-glass opacities. However, a wide variety of radiographic findings have been observed. The RHS is characterized by a central ground-glass opacity surrounded by a more or less complete ring of consolidation. First reported in cryptogenic organizing pneumonia, it was initially thought to be specific for this disease, but was subsequently described in a variety of neoplastic and non-neoplastic pulmonary diseases. In this manuscript, we present a case of Legionella pneumonia with a RHS.