It has been proposed that the cysts in BHD are the result of diminished stretch tolerance in the alveolar wall, as studies have shown that folliculin deficiency increases cell–cell adhesion in human bronchial epithelial cells (Kennedy, Khabibullin, & Henske, 2016; Khabibullin et al., 2014). The gene discussed is FLCN; the disease is Birt-Hogg-Dube syndrome.