Cystic lung disease associated with eosinophilic granuloma and tuberous sclerosis: air trapping at dynamic ultrafast high-resolution CT.

Thin-walled lung cysts can occur in association with advanced pulmonary eosinophilic granuloma and lymphangioleimyomatosis (LAM). In LAM, cysts occur as an isolated abnormality or in association with tuberous sclerosis. The cause of these cysts is unclear, but some investigators have postulated that they result from air trapping. To determine if lung cysts in these two diseases are associated with air trapping, the authors performed dynamic ultrafast high-resolution computed tomography (DUHRCT) during forced expiration in two patients (one with eosinophilic granuloma and one with tuberous sclerosis) with lung cysts and correlated the results with results of pulmonary function tests. DUHRCT demonstrated focal and diffuse air trapping; in some lung regions, a less than normal increase in lung attenuation during forced exhalation was evident. These studies do not allow a conclusion regarding the mechanism of cyst formation in eosinophilic granuloma and LAM-tuberous sclerosis, but they confirm the association between lung cysts and morphologic findings of air trapping.