Mycobacterium avium-intracellulare complex (MAC) infection

Imaging description There are several ways that mycobacterium avium-intracellulare complex (MAC) infections can present in the chest. The classic appearance of MAC infection is indistinguishable from that of pulmonary tuberculosis. However, there is another presentation which has been called the “non-classical” pattern that is virtually diagnostic of MAC disease [1]. This pattern is a combination of nodules and bronchiectasis (Figures 24.1 and 24.2) and has also been termed Lady Windermere's syndrome. The nodules and bronchiectasis have a tendency to be more prominent in the right middle lobe and lingula, but can be seen in any part of the lungs [1–4]. Although the nodules and bronchiectasis are often present in the same lobes, they do not have to be in order to suggest the diagnosis. The nodules may be micronodules with a centrilobular distribution or can be larger with a more random distribution. Importance Infection with nontuberculous mycobacteria is an important cause of pulmonary disease. Of the nontuberculous mycobacteria, MAC is the most common pathogen. When the disease presents as nodules and bronchiectasis, the diagnosis can be suggested based on the imaging findings.