Differential diagnosis of cystic lung diseases

A lung cyst is defined as a round parenchymal lucency or area of low attenuation with a thin wall. Although lymphangioleiomyomatosis (LAM) and Langerhans cell histiocytosis (LCH) are the most frequently encountered causes, the differential diagnosis for diseases characterised by diffuse lung cysts is broad ranging from isolated chest disorders to rare multisystem diseases. This article will illustrate and describe the spectrum of diseases associated with air cysts at high-resolution CT (HRCT), highlighting disorders in which the HRCT findings can be diagnostic.