What is the "crazy-paving" pattern?
It is a common finding at thin-section CT of the lungs, that consists of scattered or diffuse ground-glass attenuation with superimposed interlobular septal thickening and intralobular lines.
What is the differential diagnosis of the "crazy-paving" pattern on CT?
Causes: infection (especially pneumocystis jiroveci pneumonia), neoplasm (lepidic-predominant adenocarcinoma of the lung, lymphangitic carcinomatosis), idiophatic (pulmonary alveolar proteinosis, sarcoidosis, nonspecific interstitial pneumonia, organizing pneumonia), inhalation (lipoid pneumonia), vascular (left heart failure, adult respiratory distress syndrome, pulmonary hemorrhage syndromes, pulmonary veno-occlusive disease) and iatrogenic (radiation or drug-induced pneumonitis).
How many subgroups of pulmonary alveolar proteinosis are there?
Three: idiopathic (90%), secondary (5-10%) and congenital (2%).
Bilateral areas of "crazy-paving" in a random distribution, that tend to be more consolidative in the upper right lobe and the apical portion of the lower left lobe. Subpleural sparing pattern in the lower left lobe (better seen in the coronal projection) and some traction bronchiectasis can be observed.
There is also associated mediastinal and hilar adenopathy.