In nearly all familial cases, and in about two-thirds of sporadic cases, mutation in at least one CCM gene has been identified, with overall mutation rates ranging between 53–65% for KRIT1, 15–19% for CCM2 and 10–16% for CCM3 [23,38], confirming the central roles these genes have in CCM disease [39–41]. Here, CCM2 is linked to cerebral cavernous malformation.