High-resolution computed tomography of pulmonary alveolar microlithiasis.

Pulmonary alveolar microlithiasis (PAM) is a rare disease. It has been reported predominantly in Turkey. We report a case of PAM with characteristic high-resolution computed tomography (CT) findings. A 45-year-old Taiwanese woman had progressive difficulty in breathing for 7 years. Her chest radiographs showed diffuse high-density micronodules and reticular lines that obliterated the bronchovascular bundles and the margin of the heart and diaphragm. The micronodules were scattered throughout both lung fields with basal predominance. Examination of a transbronchial lung biopsy specimen showed PAM. High-resolution CT showed a unique and characteristic calcified reticular pattern and thickening of the interlobular septa of the lung parenchyma, with predominant basal and peripheral lung distribution. Reticulonodular changes of the interlobular septa and intralobular interstitial lines associated with subpleural air cysts and paraseptal emphysema were evident. These high-resolution CT findings are pathognomonic for PAM. Thus, lung biopsy may be avoided in the presence of this characteristic finding.