We previously reported 51 BHDS families with germline mutations in BHD, and to date more than 40 unique mutations in BHD have been reported.4–16 Germline insertion or deletion of a cytosine in the hypermutable polycytosine (C8) tract in exon 11 of the BHD gene has been detected in 53% of BHDS families and is suggested as a mutation “hot spot”.6 Most BHD germline mutations are frameshift or nonsense mutations that are predicted to truncate the BHD protein, folliculin.4–16. This evidence concerns the gene FLCN and Birt-Hogg-Dube syndrome.