This central group of genes primarily involves: CAV1, CCM2, FOXF1, FZD4, PRSS23, RASA1, SMO, TIPARP, ZFPM2 and ZMIZ1. Some of these are genes known to cause vascular malformation disorders, such as HHT: CCM2 causes cerebral cavernous malformation type 2 [20] and RASA1 causes capillary malformation-arteriovenous malformation syndrome (CM-AVM) [21]. This evidence concerns the gene SMO and capillary malformation.