Pulmonary alveolar micro-lithiasis: the imageological findings and follow-up views

Objective: To study the imageological findings and the evolution of pulmonary alveolar micro-lithiasis (PAM). Methods: The clinical and imageological information of 3 siblings suffering from PAM were collected, and their imageological findings and changes in follow-up plain radiographs were analyzed retrospectively. Results: On chest radiographs, the typical 'sandstorm' pattern was shown in all 3 cases. The severity and extent of microliths and interstitial fibrosis were increased with age and clinical course by comparing with the radiographs 24 years ago. On conventional CT, bilateral diffuse micro-nodules in parenchyma were demonstrated with pulmonary window in 3 cases, concentrating in the subpleural zones of middle and lower lung fields and the areas around bronchovesicular bundles. All were associated with various degrees of fibrosis. The nodules and calcifications were visible in both lungs with mediastinal window, forming so-called flame sign and white line sign in the concentrated areas. The extents and degrees of the microliths, small cysts and interstitial fibrosis were revealed more clearly and truly on HRCT. MRI showed diffusely increased signal intensity on T1WI and lower signal intensity on T2WI in both lung fields. Conclusion: The chest radiograph was still an initial modality in detecting the disease. CT could comprehensively reveal the pathological status of the PAM and played a decisive role in the diagnosis and differential diagnosis. MRI had only limited value in evaluating the condition