A previously healthy 29-year-old male in intimate contact with dogs presented with a five-day history of high fever, chills, headache, myalgia and nonproductive cough. He also complained of sharp right-sided chest pain worse on deep inspiration. On physical examination, the patient was febrile, tachypneic and tachycardic. Inspiratory rales were heard over the right lower lung zone. Laboratory data showed a white blood cell (WBC) count of 6.6 × 109 /L with a left shift. Inflammatory markers were mildly elevated with erythrocyte sedimentation rate (ESR) 37 mm/h and C-reactive protein (CRP) 32 mg/L. A computed tomography (CT) scan of the chest revealed a 3 cm × 3 cm, well-defined and round mass surrounded by a halo of ground-glass attenuation, namely the halo sign, in the posterior basal segment of the right inferior lobe (Fig. 1). Serologic test was positive for Coxiella burnetii (C. burnetii ) by indirect immunofluorescence assay (IFA). Empirical treatment was initiated with azithromycin (0.5 g daily), which was changed to doxycycline (100 mg twice a day) for 14 days. A follow-up CT scan performed four weeks later showed total resolution of the lesions. At six-month follow-up, the patient was asymptomatic with no radiological evidence of a relapse.
- Computed tomography (CT) scan of the chest showing a 3 cm × 3 cm, well-demarcated and spherical mass in the posterior basal segment of the right inferior lobe surrounded by a wide zone of ground-glass opacities (arrows), the halo sign.
Pneumonia is one of the cardinal manifestations of Q fever, which caused by C. burnetii infection.11 Voloudaki AE, Kofteridis DP, Tritou IN, Gourtsoyiannis NC, Tselentis YJ, Gikas AI. Q fever pneumonia: CT findings. Radiology. 2000;215:880-3. Q fever is probably the most common cause of round pneumonia in adults.22 Antón E. A frequent error in etiology of round pneumonia. Chest. 2004;125:1592-3. The halo sign refers to a zone of ground-glass attenuation surrounding the circumference of a pulmonary nodule or mass on CT images.33 Pinto PS. The CT halo sign. Radiology. 2004;230:109-10.,44 Parrón M, Torres I, Pardo M, Morales C, Navarro M, Martínez-Schmizcraft M. The halo sign in computed tomography images: differential diagnosis and correlation with pathology findings. Arch Bronconeumol. 2008;44:386-92. It has been attributed to hemorrhagic lesions mainly caused by an infectious process.11 Voloudaki AE, Kofteridis DP, Tritou IN, Gourtsoyiannis NC, Tselentis YJ, Gikas AI. Q fever pneumonia: CT findings. Radiology. 2000;215:880-3.C. burnetii infection can exceptionally manifest with a halo sign, which is caused by the infiltration of inflammatory cells and exudates into the lung.44 Parrón M, Torres I, Pardo M, Morales C, Navarro M, Martínez-Schmizcraft M. The halo sign in computed tomography images: differential diagnosis and correlation with pathology findings. Arch Bronconeumol. 2008;44:386-92. Importantly, the halo sign is a useful diagnostic clue and may be good evidence of Q fever pneumonia.
Acknowledgement
This work was partly supported by the Medical Education Research Project of Shanghai Jiao Tong University School of Medicine (No. YB130910).
REFERENCES
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1Voloudaki AE, Kofteridis DP, Tritou IN, Gourtsoyiannis NC, Tselentis YJ, Gikas AI. Q fever pneumonia: CT findings. Radiology. 2000;215:880-3.
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2Antón E. A frequent error in etiology of round pneumonia. Chest. 2004;125:1592-3.
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3Pinto PS. The CT halo sign. Radiology. 2004;230:109-10.
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4Parrón M, Torres I, Pardo M, Morales C, Navarro M, Martínez-Schmizcraft M. The halo sign in computed tomography images: differential diagnosis and correlation with pathology findings. Arch Bronconeumol. 2008;44:386-92.
Publication Dates
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Publication in this collection
Mar-Apr 2015
History
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Received
13 Oct 2014 -
Reviewed
16 Nov 2014 -
Accepted
17 Dec 2014
