A 28-year-old woman with stable hepatosplenomegaly (diagnosed at the age of 2-3 years) presented with a one-year history of progressive dyspnoea. She denied other pulmonary symptoms. The patient had a younger sister, aged 25 years, who had also had hepatosplenomegaly since early childhood and complained of mild dyspnoea. Physical examination in both sisters confirmed hepatosplenomegaly. High-resolution computed tomography performed in both sisters (figure 1) showed the same aspects, characterised by thickening of the interlobular septa and intralobular interstitium in association with small foci of ground-glass opacity.