Pulmonary nocardiosis is a rare but potentially serious infection typically in immunosuppressed patients (ISPs). It is also known to occur in immunocompetent patients (ICPs). However, little is currently known regarding the clinical characteristics and radiographic findings of pulmonary nocardiosis specifically in ICPs. In this study, 30 patients with pulmonary nocardiosis were identified and 10 were considered to be colonized. Of all patients with pulmonary nocardiosis, 12 patients were ICPs and 18 were ISPs. Although half of ISPs were infected by Nocardia nova, ICPs were affected by various Nocardia species. Compared with ISPs, chest CT findings of ICPs showed a higher prevalence of bronchiectasis (67% vs 6%, p < .01) and centrilobular nodular opacities (67% vs 11%, p < .01), both of which are often seen in pulmonary nontuberculous mycobacterial disease. Additionally, nontuberculous mycobacterium was isolated from 6 of 21 ICPs with positive Nocardia species culture. Therefore, we recommend that physicians carefully differentiate pulmonary nocardiosis from pulmonary nontuberculous mycobacterial disease in ICPs.
