We describe the case of a 33-year-old woman who presented with a pattern of diffuse micronodular opacities with centrolobular distribution at high resolution chest tomography (HRCT) performed after exposure to the smoke of a home fire. An abdominal CT scan showed the presence of 3 rounded hypodense lesions in the spleen parenchyma. A bronchoalveolar lavage (BAL) was performed, showing the presence of lipid laden cells in the aspirated fluid. A video-assisted thoracoscopic biopsy confirmed the presence of the foamy cells filling the alveolar spaces and showed a preserved background pulmonary architecture; the bronchiolar epithelium presented a cytoplasm with a particularly clear colour. Foam cells were present in the bone marrow aspirate too, that contained also sea-blue histiocytes. These data induced us to consider the diagnosis of a metabolic storage disorder, in the first instance Niemann-Pick type B, that was confirmed by low acid lysosomal sphingomyelinase activity on cultured fibroblasts: 5.22 nmol/mg prot/h (n.v. 92 +/- 18.2). Lung involvement is an important complication of Niemann-Pick disease, presenting with the clinical and radiological features of a diffuse lung disease.