[Hypersensitivity pneumonitis. A series of nine cases with surgical lung biopsy].

In a series of nine patients with histopathological diagnosis of hypersensitivity pneumonitis, we retrospectively evaluated clinical data, exposure related factors, pulmonary function tests and chest computed tomography scans. A restrictive abnormality with reduction of diffusion capacity for carbon monoxide was mainly found. Chest scans showed fibrotic patterns in most cases; ground glass attenuation areas with mosaic pattern and consolidation in the rest. Exposure to avian antigens, cereal grains and air conditioners contaminated with fungi yeasts and bacteria, were suspected from clinical data in two-thirds of the cases. Since there are no unique features that allow differentiation from other interstitial lung diseases, a high clinical suspicion is required and a careful search of environmental exposure to possible antigens is needed that, together with clinical, radiological and pathological data, may lead to diagnosis.