While some cases can be attributed to several rare inherited monogenic disorders caused by mutations in FBN1, COL3A1, CBS, SERPINA1 and TSC1/TSC2 genes [2–6], a significant proportion of PSP cases are caused by germline mutations of FLCN gene, a causative gene of Birt-Hogg-Dube syndrome (BHD, OMIM #135150) [7–11]. Here, CBS is linked to Birt-Hogg-Dube syndrome.