RESUMEN
Pulmonary alveolar proteinosis is a very rare interstitial lung disease caused by abnormal intra-alveolar surfactant accumulation. Usually, it appears as a "crazy-paving" pattern on high-resolution computed tomography. The image is so typical, that together with the characteristic bronchoalveolar lavage examination with presence of Periodic Acid Schiff positive substance is sufficient for establishing diagnosis, without histological confirmation. We present the case of the young woman with severe dyspnoea suspected of acute hypersensitivity pneumonia. The computed tomography showed numerous intralobular nodules uniformly distributed troughout the lungs. Treatment by corticosteroids had no clinical effect and next computed tomography showed progression. Despite the high risk of complications (patient had a respiratory failure), a surgical lung biopsy was performed and the histopathological diagnosis of pulmonary alveolar proteinosis was made. The whole lung lavage procedure performed twice caused regression of radiological lesions and respiratory failure.