high-resolution computerized tomography changes in diffuse parenchymal lung disease from chronic hypersensitivity pneumonitis related to bird antigen

Background: Chronic hypersensitivity pneumonitis (HP) is the most common cause of diffuse parenchymal lung disease (DPLD) in India. There is no data regarding the avian antigen exposure-associated DPLD from the country. Methods: Chronic HP from exposure to avian antigen was diagnosed when the high resolution computerized tomography (HRCT) showed features for HP and was supported by the history of exposure to pigeons, the presence of precipitin antibodies (IgG) to avian antigen in high titre with negative rheumatoid factor, antinuclear antibody, and no clinical clue for a collagen vascular disease. The HRCT changes were noted on Likert scale (0–5) in terms of affection of peripheral and/or axial involvement, reticulation, honeycombing, haze, mosaic, traction bronchiectasis, pleural reactions, features of pulmonary hypertension, and air cysts. Cardiomegaly and independent cardiac chamber enlargement were also recorded. Results: The lower lobes were predominantly (65.6%) affected with similar frequency (78.1) of peripheral and axial parenchymal affection. The parenchymal changes in HRCT were haze or ground-glass opacity (100%), mosaic appearance (93.75%), reticulations (68.75%), traction bronchiectasis (34.3%), air cysts (21.8%), and honeycombing (9.37%). Pleural reactions, though not described so far, were found in 50% of cases. Features of pulmonary hypertension (87.5%), cardiomegaly (50%), left and right atrial enlargement (81.2% and 78.1%), and right ventricular enlargement (31.2%) were the common echocardiography findings. Conclusion: Chronic HP from avian exposure shows predominantly lower lobe involvement with haze, reticulation, features of pulmonary hypertension, and pleural reactions as common HRCT findings. The likelihood of pulmonary hypertension appears high and although honeycombing is often present, the classical UIP pattern has not been found.