Nontuberculous mycobacterial (NTM) infections of the lungs often occur in the context of preexisting lung disease, especially chronic obstructive pulmonary disease (COPD), bronchiectasis, pneumoconiosis, cystic fibrosis, and previous tuberculosis [1-4]. As a result, the clinical manifestations of NTM lung disease are often similar to those of the underlying disease. These include cough, fatigue, malaise, fever, weight loss, dyspnea, hemoptysis, and chest discomfort. These same symptoms are also present in patients with NTM lung disease who do not have preexisting pulmonary disease. (See "Overview of nontuberculous mycobacterial infections in HIV-negative patients".)
The possible presence of NTM lung disease often arises clinically when NTM are identified on sputum culture from a patient under evaluation for tuberculosis. The laboratory findings used to confirm the diagnosis of NTM infection in this setting will be reviewed here. The epidemiology, pathogenesis, and treatment of NTM are discussed separately. (See "Epidemiology of nontuberculous mycobacterial infections" and "Pathogenesis of nontuberculous mycobacterial infections" and "Treatment of nontuberculous mycobacterial infections of the lung in HIV-negative patients".)
The radiographic findings of nontuberculous mycobacterial (NTM) lung disease are variable, depending in part upon the species. Findings consistent with NTM pulmonary infection on chest radiograph or high-resolution computed tomography scan include infiltrates (usually nodular or reticulonodular), cavities, multifocal bronchiectasis, and/or multiple small nodules. (See "Overview of nontuberculous mycobacterial infections in HIV-negative patients".)
The radiographic pattern of disease can usually be separated into predominantly cavitary versus nodular/bronchiectatic. Some generalizations can be made:
- Cavitary disease in the upper lung zones, similar to pulmonary tuberculosis, is seen in approximately 90 percent of patients with M. kansasii infection and perhaps 50 percent of those with Mycobacterium avium complex (MAC) infection. The cavities caused by these organisms tend to have thinner walls and less surrounding parenchymal opacity than those caused by M. tuberculosis [5,6].
- At least 50 percent of patients with MAC lung disease have radiographic abnormalities characterized by nodules associated with bronchiectasis or nodular/bronchiectatic disease. The nodules and bronchiectasis are usually present within the same lobe and occur most frequently in the right middle lobe and lingula .