Most individuals with BHD who had pulmonary cysts (six of seven) and spontaneous pneumothorax (four of five) had disease-causing FLCN variants in exons 11 and 12, consistent with previous correlations between pulmonary features and pathogenic variants in exon 9 and greater (18, 20). This evidence concerns the gene FLCN and Birt-Hogg-Dube syndrome.