FLCN and Spontaneous pneumothorax: Birt-Hogg-Dubé (BHD; ORPHA122) syndrome is an autosomal dominant disorder caused by loss-of-function mutations in the folliculin (FLCN) gene and characterized by skin fibro-folliculomas, multiple lung cysts lined by fibrous band (in up to 90% of cases), spontaneous pneumothorax, and renal cancer [63].