[Chest high resolution CT features of extrinsic allergic alveolitis and its diagnostic value]

To summarize the chest high-resolution CT (HRCT) features of the patients with extrinsic allergic alveolitis (EAA).

We analyzed the images of chest HRCT of 34 patients diagnosed as EAA at our hospital from February 2001 to August 2009.

All patients had a history of environmental exposure. The duration of intermittent or continuous antigen exposure was from 3 months to 13 years. Two patients showed acute clinical manifestations. There were 22 sub-acute and 10 chronic cases. Acute EAA was characterized by ground-glass opacities, air trapping and/or mosaic sign on HRCT. The HRCT features of subacute EAA included patchy ground-glass opacities with mosaic sign (n = 11, 50.0%) and diffusely distributed centrilobular nodules (n = 7, 31.8%) with mosaic sign (n = 4, 18.2%). All patients with chronic EAA had reticular and honeycombing lesions on HRCT. There were 3 cases with ground-glass opacities, 3 with mosaic sign, and 3 with centrilobular nodules.

The typical findings of chest HRCT are helpful for making a diagnosis and differential diagnosis of EAA.