Alveolar microlithiasis: an uncommon cause of the crazy paving pattern

Alveolar microlithiasis is an uncommon disease of unknown etiology characterized by the presence of multiple, predominantly subpleural, intra-alveolar microcalcifications. We present a case in which the high-resolution CT images show diffuse pulmonary microcalcifications together with patchy areas of ground glass attenuation associated to marked thickening of the interlobular septa, all of which taken together constitute the crazy paving pattern. This pattern is not specific for alveolar microlithiasis; it has also been reported in other entities, including alveolar proteinosis, lipoid pneumonia, and bronchial alveolar carcinoma.