An 80-year-old man with rapidly progressive dyspnoea. A chest radiograph and CT were undertaken. The chest radiograph showed a patchy distribution of areas with consolidation. There was also a fine reticular pattern, most pronounced in the periphery of both lungs (Fig. 4a ). Chest CT, performed to rule out acute pulmonary embolism, was negative for the presence of lung emboli. A crazy-paving pattern with a scattered distribution of ground-glass opacities and a linear pattern superimposed, with multiple small irregular lines, was visible. Traction bronchiectasis was seen in the periphery of both lungs (Fig. 4b) . Chest radiograph showed a reticular pattern that was most pronounced in the central parts of the lungs. There was also a decrease in the lung translucency centrally in both lungs. Heart and central vessels were normal. There was no pleural effusion. b On CT, a patchy distribution of a crazy-paving pattern was visible. The lines corresponded to a deposition of material within the airspaces at the borders of the acini (1) in the secondary pulmonary lobules, but also along the interlobular (2) and intralobular septa (3): the periacinar pattern. c Radiological-histopathological correlation. Histopathological evaluation of a specimen out of the right lung showed amorphous eosinophilic material in the alveoli (*) positive on periodic acid Schiff (PAS) staining. This material corresponded to deficient surfactant. Filling of the alveoli (*) was responsible for the ground-glass appearance on CT. When the airspaces adjacent to the inter-and intralobular septa (black arrow) and to the alveolar walls filled, the periacinar pattern became visible On histology, thickening of the interstitium with variable degrees of severity was seen, leaving some alveolar septa almost completely normal, whereas others were thickened. Fibrinous exudates, honeycombing and mild inflammatory alveolitis were also present (Fig. 4c) .