Rare mutations in the folliculin gene (FLCN) have been implicated in two genetic syndromes with shared pulmonary manifestations of spontaneous pneumothorax and lung cyst formation: Birt-Hogg-Dubé syndrome (BHD, MIM 135150) and familial spontaneous pneumothorax (FSP, MIM 173600)[1]. This evidence concerns the gene FLCN and familial spontaneous pneumothorax.