Original articleClinical characteristics of pulmonary Mycobacterium scrofulaceum disease in 2001–2011: A case series and literature review
Introduction
The incidence of pulmonary nontuberculous mycobacterial (NTM) infections has gradually increased [1]. Of >150 NTM species, Mycobacterium avium complex (MAC) is the pathogen most often associated with pulmonary NTM infection, followed by rapid-growing mycobacteria (RGM) in the USA, RGM and Mycobacterium xenopi in Europe, and RGM in Asia [2], [3]. Other NTM species are relatively uncommon and have been described in only a few reports [2].
Mycobacterium scrofulaceum is a slow-growing Runyon II mycobacterial species distributed across a wide range of environments, including house dust, tap water, and soil [4]. In 1980, M. scrofulaceum accounted for 2–3% of all mycobacterial isolates recovered from clinical samples in the USA [5]. Although M. scrofulaceum is a well-known pediatric cervical lymphadenitis-associated pathogen [6], pulmonary M. scrofulaceum disease is rare and has been described in a few English language reports.
Notably, a case series published in 1999 described the characteristics of pulmonary M. scrofulaceum disease in South African gold miners, particularly the appearance of cavitation on radiographic images and a medical history of silicosis or prior tuberculosis scarring [7]. It is unknown why such a relatively large number of reported M. scrofulaceum cases (n = 41) occurred in South Africa. However, this aberrant incidence may be related to an occupational history of dust inhalation leading to the development of silicosis in gold miners, consistent with a previous report in which exposure to dust was described as a risk factor for NTM lung disease, including pulmonary M. scrofulaceum disease [8]. On the other hand, little is known about the clinical features of pulmonary M. scrofulaceum disease in the absence of dust exposure or silicosis.
Herein, we investigated clinical features and outcomes of 8 cases of pulmonary M. scrofulaceum disease encountered at our 2 institutions in 2001–2011. We have also provided a review of previously reported cases of pulmonary M. scrofulaceum disease and compared the clinical features of cases with or without silicosis or dust exposure.
Section snippets
Patients and methods
The medical records of all adult patients who met the diagnostic criteria of pulmonary M. scrofulaceum disease at 2 institutions, Keio University Hospital and National Center for Global Health and Medicine Center Hospital, from 2001 to 2011 were retrospectively reviewed. The diagnostic criteria were based on the American Thoracic Society/Infectious Disease Society of America (ATS/IDSA) guidelines [4]. In brief, a diagnosis of M. scrofulaceum required the presence of pulmonary symptoms or
Case series
During the aforementioned period, we diagnosed 8 cases of pulmonary M. scrofulaceum disease at our institutions. Table 1, Table 2 present the background and clinical characteristics of each case, respectively. The median age at diagnosis was 68 years. Seven patients were men; 5 patients (all men) had a smoking history. All patients except for No. 8 had an underlying pulmonary disease such as chronic obstructive pulmonary disorder (COPD; No. 4 and No. 6), a history of pulmonary tuberculosis (No.
Discussion
Herein, we have reported 8 cases of pulmonary M. scrofulaceum disease encountered at our 2 institutions, along with 23 cases identified through a literature review. From this case series, we have confirmed 2 important clinical features common to both the cases encountered at our institutions, and those identified in the literature: first, pulmonary M. scrofulaceum disease usually affects middle-aged and elderly male patients with underlying pulmonary diseases such as COPD, a history of
Conflict of interest
The authors declare that they have no competing interests.
Acknowledgments
The authors thank Satoru Ishii (National Center for Global Health and Medicine, Tokyo, Japan) for assistance in acquisition of data.
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