British Journal of Radiology (2007) 80, e21-e23
© 2007 British Institute of Radiology
doi: 10.1259/bjr/30339154
Hantavirus pulmonary syndrome: high-resolution CT findings in one patient
E L Gasparetto, MD
1
T Davaus, MD
1
D L Escuissato, MD
1 and
E Marchiori, MD
2
Departments of Diagnostic Radiology, 1University of Paraná and 2University of Rio de Janeiro, Brazil
Correspondence: Emerson L Gasparetto, Av. Silva Jardim 296, Ap. 502, 80230-000 Curitiba, PR, Brazil. E-mail: egasparetto{at}gmail.com
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Abstract
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Physical examination demonstrated petechiae, leg oedema and mild dyspnoea. Chest radiograph showed minimal bilateral hazy increased opacification, mainly on the right side, and small bilateral pleural effusions. High-resolution CT demonstrated extensive bilateral ground-glass opacities most severe in the middle and lower lung zones. Also noted were a few slightly thickened interlobular septa, a few poorly defined small nodules, bronchial wall thickening and small bilateral pleural effusions. Blood tests revealed high leukocyte and low platelet counts. Renal function was normal. Serological test (ELISA) for hantavirus using SNV (Sin Nombre virus) antigen was positive. The patient received supportive treatment, gradually improved, and was discharged 10 days after hospital admission. His symptoms completely resolved and follow-up radiographs returned to normal.
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Introduction
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Hantaviruses are rodent-borne single-strand RNA viruses responsible for the hantavirus pulmonary syndrome, a condition first recognized in 1993 in the south-western USA [1, 2]. Since then, hantavirus pulmonary syndrome has been described in several countries in North and South America, Europe, and Asia [3–5].
The radiographic manifestations range from mild bilateral interstitial changes to extensive bilateral consolidation [6, 7]. The interstitial changes consist of peribronchial cuffing, septal lines and hazy perihilar opacities consistent with interstitial pulmonary oedema [6, 7]. The findings can resolve, or progress rapidly to extensive bilateral consolidation secondary to non-cardiogenic pulmonary oedema. Bilateral pleural effusions are seen in approximately 75% of patients [6, 7].
To our knowledge, the CT manifestations of hantavirus pulmonary syndrome have not been previously described. We report the high resolution CT findings in one patient.
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Case report
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The 19-year-old in this case lived near a forest containing rodents, where previous hantavirus infection had occurred. He presented with a 6-day history of fever, headache, vomiting and myalgia. Physical examination demonstrated petechiae, leg oedema and mild dyspnoea.
Chest radiograph showed minimal bilateral hazy increased opacification, mainly on the right side, and small right pleural effusion (Figure 1a
). High-resolution CT (1.5 mm collimation, edge enhancing algorithm) demonstrated extensive bilateral ground-glass opacities most severe in the middle and lower lung zones (Figure 1b,c). Also noted were a few slightly thickened interlobular septa, a few poorly defined small nodules, bronchial wall thickening and small bilateral pleural effusions (Figure 1b,c).
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Figure 1. 19-year-old male patient with hantavirus pulmonary syndrome. (a) Chest radiograph shows hazy increased opacity involving mainly the right lung and small right pleural effusion. (b) High-resolution CT (1.5 mm collimation, edge enhancing algorithm) at the level of the right upper lobe bronchus shows bilateral ground-glass opacities, peribronchial thickening (curved arrow), a few poorly defined small nodules (straight arrows) and mild septal thickening (arrowheads). (c) High-resolution CT at the level of the bronchus intermedius shows extensive bilateral ground-glass opacities, peribronchial thickening (curved arrow) and a few poorly defined small nodules (straight arrows).
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Blood tests revealed high leukocyte and low platelet counts. Renal function was normal. Sputum and bronchoalveolar lavage specimens and cultures were negative. Serological tests for HIV, Chlamydia pneumoniae, dengue and leptospirosis were all negative. Because two previous cases were seen recently at our institution, a serological test (ELISA) for hantavirus using SNV (Sin Nombre virus) antigen was performed and found to be positive.
The patient received supportive treatment, gradually improved, and was discharged 10 days after hospital admission. 1 month later, his symptoms completely resolved and follow-up radiographs returned to normal.
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Discussion
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Hantaviruses are rodent viruses which can affect humans after inhalation of aerosolized virus particles from urine, saliva, or dried excreta of rodent reservoirs, most commonly deer mice and rats [1, 2, 4]. The hantavirus causes haemorrhagic fever with renal failure from five different viruses, with the Sin Nombre virus only detected in early 90s, which is usually associated with prominent pulmonary involvement. The hantavirus pulmonary syndrome typically develops after an incubation period of 9–35 days. The concept of an occupation at risk in 20–49 year old men working in forests, agriculture, living near a forest or in contact with wood in an endemic area has not always been found. The infection is usually characterized by three stages: prodromal stage cardiopulmonary stage and convalescent phase [1, 8]. The most common clinical manifestations during the prodromal phase are fever, myalgia and malaise. This is followed by the cardiopulmonary stage characterized by progressive shortness of breath, often followed by rapid clinical deterioration with progressive respiratory failure and hypotension. The infection progresses quickly and is associated with a high mortality rate (more than 50%). The convalescent phase is characterized by rapidly improving oxygenation, haemodynamic stabilization and diuresis [6, 7].
The radiographic manifestations were first described by Ketai et al based on a review of 16 patients with hantavirus pulmonary syndrome seen in New Mexico [6]. The most common findings at presentation were features of interstitial pulmonary oedema seen in 14 (88%) of the 16 patients. 11 (69%) of the 16 patients progressed to airspace oedema and 7 (43%) died. Lung specimens obtained at autopsy showed a pattern of endothelial leak with minimal epithelial injury. Other studies discussing the histological findings of hantavirus pulmonary syndrome demonstrated mild to moderate interstitial pneumonitis, with mononuclear infiltration and congestion, and oedema [1, 2, 8].
Boroja et al reviewed the findings in 20 patients with Hantavirus pulmonary syndrome seen in Alberta, Canada [7]. They identified two distinct patterns of presentation. The first pattern, seen in 13 of 20 patients, was characterized by a fulminant clinical course and need for intensive care support. These patients presented with bilateral airspace consolidation or showed rapid progression from bilateral interstitial changes to bilateral interstitial pattern and airspace consolidation with pleural effusions. Six (46%) of the 13 died within a few days of presentation. The second pattern, seen in seven of 20 patients, was characterized by mild clinical symptoms and chest radiographs showing normal findings or minimal bilateral abnormalities. All these patients recovered.
The radiological differential diagnosis includes pulmonary oedema, bacterial and viral pneumonia. In patients with hantavirus pulmonary syndrome, the clinical history, when added to the laboratory and radiographic findings, may suggest the diagnosis. However, viral-specific diagnostic tests, such as serological tests, reverse transcription or polymerase chain reaction, are required to confirm the diagnosis of hantavirus pulmonary syndrome [7, 9, 10]. Our patient presented with a flu-like clinical history, associated with low platelets and positive serological test (ELISA) for hantavirus. The patient demonstrated the limited form of presentation of hantavirus pulmonary syndrome, with mild clinical symptoms, minimal radiographic abnormalities, and gradual improvement on supportive treatment. High-resolution CT was helpful in demonstrating the presence of extensive bilateral abnormalities that were difficult to visualize on the radiograph.
The high-resolution CT findings in our patient consisted of bilateral ground glass opacities, mild septal thickening, and occasional poorly defined small nodular opacities. These findings are non-specific, being seen in a number of other conditions including pulmonary haemorrhage, pulmonary oedema and diffuse pneumonia.
In conclusion, hantavirus pulmonary syndrome is a rare disease, which may present with bilateral areas of ground-glass attenuation, thickened interlobular septa, poorly defined small nodules and bronchial wall thickening at the high-resolution CT. These findings are unspecific, and the differential diagnosis with other pulmonary infectious and non-infectious diseases should be considered.
Received for publication July 11, 2005.
Revision received February 4, 2006.
Accepted for publication February 9, 2006.
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References
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Abstract
Introduction
