Pulmonary nocardiosis: computed tomography features at diagnosis

To review the computed tomography (CT) imaging features of pulmonary nocardiosis (PN) at the time of initial presentation.

All patients from 1991 to 2008 with PN were identified (n=105). Patients without CT scan available at initial presentation were excluded (n=52). For the remaining 53 patients, standardized radiographic features were recorded. The patients were grouped by predisposing condition. Analysis includes descriptive summary statistics as well as associations among radiographic findings, associated findings, and host characteristics. Parametric and nonparametric statistical methods were used.

Median age of the patients was 52 years (range, 6 to 82 y). Some form of immunosuppression was present in 83% of the cases. Preexisting structural abnormalities of the lung were uncommon (bronchiectasis, 7; chronic obstructive pulmonary disease, 3). Twenty (38%) patients had interstitial opacities. Airspace disease was seen in 34 (64%) cases. Thirty (57%) cases revealed discrete nodules, 25 patients had 1 to 6 nodules (mean, 2), and 5 patients had fewer than 6 nodules, with the mean size of the largest nodule being 1.67 cm. Masses were seen in 11 patients (21%), 9 of whom had concomitant nodules. Cavitary lesions, including nodules, masses, or airspace disease, occurred in 40% of the cohort. Mediastinal lymphadenopathy was present in 8 (15%) patients. Fifteen patients (28%) had pleural effusions; the effusions were unilateral in 10 patients. Analysis of radiographic associations with patient groups found discrete nodules to be more often associated with immunosuppression compared with the nonimmunosuppressed group (66% vs. 11%; P=0.0067).

The CT presentation of PN is heterogeneous. Airspace disease appeared most frequently (in 64% of the cases), and nodules were present in 57% of the cases. Nocardiosis should be considered in the differential diagnosis of immunosuppressed patients with new nodules or masses.