대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Legionella pneumonia

Radiologic Findings

Chest radiograph demonstrates mass like opacity in left middle lung field. Chest CT demonstrates consolidation with air-bronchogram and GGO with surrounding consolidation (reverse halo sign) in LUL. Urinary antigen for Legionella was positive and the diagnosis of Legionella pneumonia was made. The patient was given levofloxacin and discharged 6 days after admission.

Brief Review

Legionella is a genus of pathogenic Gram-negative bacteria that include the species L. pneumophila, causing legionellosis (all illnesses caused by Legionella) including a pneumonia-type illness called Legionnaires’ disease and a mild flu-like illness called Pontiac fever. Legionella is found naturally in freshwater environments such as lakes and streams. It can become a health concern when it grows and spreads in human-made building water systems such as: Showerheads and sink faucets, cooling towers, hot water tanks and heaters, and large plumbing systems.
Although otherwise nonspecific, typical computed tomography (CT) features of legionella pneumonia include airspace consolidation and ground-glass opacities. However, a wide variety of radiographic findings have been observed. Those with extensively consolidated lesions can have associated cavitation, while pleural effusions can be common and are occasionally seen, even in the absence of lung field infiltrates. Rarely, as in this case, Legionella pneumonia can present with reversed halo sign. Radiographic appearances often lag behind the clinical picture and there can be deterioration on imaging despite clinical improvement. Resolution of infiltrates may be slow, and the tendency for delayed improvement should be considered before initiating any further

Please refer to

Case 364, Case 474,

KSTR Imaging Conference 2000  Case 5,

References

1. Mittal S, Singh AP, Gold M, Leung AN, Haramati LB, Katz DS. Thoracic Imaging Features of Legionnaire's Disease. Infect Dis Clin North Am. 2017;31:43-54.
2. Yu H, Higa F, Hibiya K, et al. Computed tomographic features of 23 sporadic cases with Legionella pneumophila pneumonia. Eur J Radiol. 2010;74:e73-e78.
3. Godoy MC, Viswanathan C, Marchiori E, et al. The reversed halo sign: update and differential diagnosis. Br J Radiol. 2012;85:1226-1235.

Keywords

lung, pneumonia, Legionella ,