Radiology of pulmonary Mycobacterium avium-intracellulare complex

Although the radiographic appearance of pulmonary MAC infection in the immunocompetent host can be varied, there are several generalizations that can be made. The classic radiographic appearance is indistinguishable from that of pulmonary tuberculosis. The classic form is seen most commonly in males and is typically associated with other predisposing diseases, especially chronic obstructive pulmonary disease. Most patients have upper lobe disease with associated pleural thickening. Widespread disease is common, as is cavitation. Pleural effusions and adenopathy are uncommon. The Lady Windermere syndrome is a special form of pulmonary MAC seen primarily in middle-aged and elderly women. The radiographic findings are bronchiectasis and small nodules, predominately located within the middle lobe and lingula. The combination of bronchiectasis involving exclusively, or primarily, the right middle lobe and lingula is highly suggestive of pulmonary MAC, even in the face of negative sputum cultures. Pulmonary infection with MAC in the immunocompromised patient generally reflects a widespread systemic disease. As such, the radiographic appearance is highly variable. Diffuse pulmonary opacities and adenopathy are common features. Plain radiographs are frequently normal despite active pulmonary infection. Regardless of the clinical situation, pulmonary MAC infection is often omitted from the radiographic differential even when the appearance is characteristic. In general, when pulmonary abnormalities are identified that are consistent with a granulomatous infection, pulmonary MAC needs to be considered along with tuberculosis and fungal infection. Especially with pulmonary MAC, radiographic stability over several years does not exclude active disease. The radiographic appearance may be suggestive of the diagnosis of pulmonary MAC, but correlation with the clinical and microbiological data is necessary to confirm the diagnosis.