Pathology.—Histologically, DIP is characterized by the widespread accumulation of an excess of macrophages in the distal airspaces. The macrophages are uniformly distributed, unlike in respiratory bronchiolitis–interstitial lung disease, in which the disease is conspicuously bronchiolocentric. Interstitial involvement is minimal. Most cases of DIP are related to cigarette smoking, but a few are idiopathic or associated with rare inborn errors of metabolism (5).
Radiographs and CT scans.—Ground-glass opacity is the dominant abnormality and tends to have a basal and peripheral distribution (Fig 22). Microcystic or honeycomb changes in the area of ground-glass opacity are seen in some cases (55). [Fleischner Society]