FLCN and pneumothorax: Birt-Hogg-Dubé syndrome (BHDS) (MIM 135150) or Hornstein-Knickenberg syndrome is an autosomal-dominant hereditary disorder associated with the germline pathogenic variant of the folliculin gene (FLCN), which causes a predisposition for the risk of benign cutaneous fibrofolliculomas, pulmonary cysts, spontaneous pneumothorax, and multiple, mainly malignant, bilateral and multifocal renal neoplasias [1, 2].