Alveolar microlithiasis

Imaging description Alveolar microlithiasis is a rare disease of unknown etiology. Histologically, it is characterized by tiny calculi (microliths) in an intra-alveolar location [1, 2]. On CT imaging, innumerable tiny (1 mm) calcified centrilobular nodules can be seen throughout the lungs (Figures 20.1–20.4). The nodules tend to cluster in a perilymphatic distribution and can be seen on CT as high attenuation along the interlobular septa, bronchovascular bundles, and in the subpleural lung [1–3] (Figures 20.1–20.3). When the nodules are too small to be clearly identified as discrete nodules, they appear as areas of ground-glass attenuation in the lungs (Figures 20.2–20.4). When there is extensive microlithiasis, the calcifications can present as areas of “calcified” consolidation (Figure 20.1).