CORRESPONDENCE An Unusual Case of Nocardiosis Presented as a Mediastinal Mass in an Immunocompetent Patient To the Editor: The genus Nocardia is a ubiquitous group of environmental bacteria that usually manifests as an opportunistic infection in immunocompromised hosts. Immunocompetent patients usually develop localized cutaneous lesions, such as cellulitis, abscesses, or sporotrichoid forms of infection. We present an unusual case of nocardiosis that presented as a mediastinal mass in an immunocompetent patient. Case Report
A 29-year-old man, otherwise healthy, presented with recurrent episodes of fever and productive cough for a couple of months. He was treated with antibiotics for pneumonia without response. His physical exam was unremarkable. Laboratory studies revealed leukocytosis and an elevated C-reactive protein. A chest X-ray showed widening of the mediastinum and right hilum, and an alveolar opacity in the right upper lobe (Figure 1). A chest computed tomography (CT) scan showed a number of ﬁndings: a large inhomogeneous mass in the mid-mediastinum causing pressure and mass effects on the blood vessels and airways in proximity, and mediastinal lymphadenopathy (Figure 2), as well as an inhomogeneous mass-like consolidation in the right upper lobe (Figure 3). The mediastinal ﬁndings were suggestive of a neoplastic process, such as lymphoma or small cell lung cancer. The consolidation in the right upper lobe was suggestive of pneumonia, which was more compatible with the clinical picture. A biopsy
Figure 1. A chest X-ray that shows widening of the mediastinum and upper part of right hilum, and an alveolar opacity in the right upper lobe.
Figure 2. Contrast computed tomography (CT) image of the chest showing inhomogeneous mass in the mid-mediastinum, causing pressure and mass effect on the blood vessels and trachea and bronchi in proximity, and mediastinal lymphadenopathy.
from the mediastinal mass revealed an inﬂammatory process diagnostic of nocardiosis. Direct smear of a biopsy sample showed gram-positive rods suspected as Nocardia. Culture and polymerase chain reaction were positive, and the pathogen was ultimately identiﬁed as Nocardia asiatica. On antibiotic susceptibility tests, the bacteria were shown to be sensitive to imipenem, linezolid, and cotrimoxazole. An immunologic workup was conducted in suspicion of immunodeﬁciency, which included HIV status and tests for chronic granulomatous disease, all of which were negative. A brain CT scan excluded Nocardia cerebral involvement. The patient was treated with a combination of imipenem and cotrimoxazole for 3 weeks, followed by an additional 3 months with cotrimoxazole alone. On follow up, there was clinical and radiographic improvement, with near-complete regression of the pulmonary consolidation, and marked regression of the mediastinal lesion after 9 months, according to his last CT examination (Figure 4).
Figure 3. Contrast CT image of the chest showing an inhomogeneous mass-like consolidation in the right upper lobe of the lung.
American Journal of Respiratory and Critical Care Medicine Volume 189 Number 4 | February 15 2014
CORRESPONDENCE We found only two reports in the literature of nocardiosis that presented as a mediastinal mass, but in both cases the patients were immunocompromised (11, 14). In one of them, it was caused by N. asiatica (11). One other case report describes an immunocompetent patient with N. asiatica (12). n Author disclosures are available with the text of this letter at www.atsjournals.org. Maya Abu-Gazala, M.D. Ahuva Engel, M.D. Anat Stern, M.D. Ludmila Guralnik, M.D. Rambam Medical Center Haifa, Israel
Figure 4. Chest CT image 9 months later showing significant improvement in the mediastinal lesion.
The genus Nocardia is a ubiquitous group of environmental bacteria that usually manifests as an opportunistic infection in immunocompromised hosts. However, up to one-third of patients with nocardiosis are immunocompetent (1, 2). Nocardia can be found in soil, decomposing vegetation, and other organic matter, as well as in fresh and salt water (1). Pulmonary nocardiosis is the most common clinical presentation of infection because inhalation is the primary route of bacterial exposure (1). The chest radiograph can be variable, displaying focal or multifocal disease with nodular and/or consolidation inﬁltrate as well as cavitary lesions (3, 4). Extrapulmonary nocardiosis is relatively common and can occur through hematogenous dissemination or contiguous spread of necrotizing pneumonitis into the pleura, pericardium, mediastinum, and vena cava (1). Immunocompetent patients usually develop localized cutaneous lesions, such as cellulitis, abscesses, or sporotrichoid forms of infection (5). N. asiatica is a rare subtype of Nocardia species. The few case reports available in the literature have shown that N. asiatica causes brain abscesses (6), skin infections (7), pulmonary infections (8, 9), and septic bursitis (10). There is one case report of N. asiatica presenting as an anterior mediastinal cystic mass (11), and one other case report describes an immunocompetent patient with N. asiatica (12). In a study from Taiwan that evaluated antibiotic susceptibilities of various species of Nocardia, 7 out of 151 Nocardia isolates were N. asiatica (13). Regarding antibiotic therapy, there are no guidelines, as infection with this Nocardia species is rare. Treatment of pulmonary nocardiosis is usually with combined antibiotics including imipenem, cotrimoxazole, or amikacin (7). In a study that evaluated in vitro antibiotic susceptibilities of different Nocardia species, all seven of the N. asiatica isolates examined were susceptible to imipenem, cotrimoxazole, amikacin, and linezolid (13). Our patient was treated with imipenem and cotrimoxazole according to the in vitro susceptibility pattern, and had a signiﬁcant clinical and radiological response. Our case is unusual because it presented as a mediastinal mass in an immunocompetent patient and was caused by a rare species of Nocardia. Correspondence
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