FLCN and Spontaneous pneumothorax: According to Table 7, the top 10 keywords with the highest frequency in 2001–2021 are Birt-Hogg-Dubé syndrome (347), spontaneous pneumothorax (168), mutation (159), renal cell carcinoma (119), family (83), folliculin (83), BHD gene (68), tumor (67), cancer (66), fibrofolliculoma (66).