Abstract
Objective Pulmonary nocardiosis frequently develops as an opportunistic infection in patients with malignant tumor and is treated with steroids. This study was performed to clarify the clinical features of pulmonary nocardiosis in Japan. Methods The patients definitively diagnosed with pulmonary nocardiosis at our hospital between January 1995 and December 2015 were retrospectively investigated. Results Nineteen men and 11 women (30 in total) were diagnosed with pulmonary nocardiosis. Almost all patients were complicated by a non-pulmonary underlying disease, such as malignant tumor or collagen vascular disease, or pulmonary disease, such as chronic obstructive pulmonary disease or interstitial pneumonia, and 13 patients (43.3%) were treated with steroids or immunosuppressors. Gram staining was performed in 29 patients, and a characteristic Gram-positive rod was detected in 28 patients (96.6%). Thirty-one strains of Nocardia were isolated and identified. Seven strains of Nocardia farcinica were isolated as the most frequent species, followed by Nocardia nova isolated from 6 patients. Seventeen patients died, giving a crude morality rate of 56.7% and a 1-year survival rate of 55.4%. The 1-year survival rates in the groups with and without immunosuppressant agents were 41.7% and 59.7%, respectively, showing that the outcome of those receiving immunosuppressants tended to be poorer than those not receiving them. Conclusion Pulmonary nocardiosis developed as an opportunistic infection in most cases. The outcome was relatively poor, with a 1-year survival rate of 55.4%, and it was particularly poor in patients treated with immunosuppressant agents. Pulmonary nocardiosis should always be considered in patients presenting with an opportunistic respiratory infection, and an early diagnosis requires sample collection and Gram staining.