Familial CCM (about 20% of CCM patients) occurs as a condition with autosomal dominant transmission mode caused by loss-of-function mutations in one of the 3 CCM genes: CCM1/KRIT1, CCM2/Malcavernin/OSM and CCM3/PDCD10 (Bergametti et al., 2005; Denier et al., 2004; Laberge et al., 1999; Liquori et al., 2003). The gene discussed is CCM2; the disease is cerebral cavernous malformation.