Patients with familial CMs harbor biallelic loss-of-function (LOF) mutations in one of three cerebral cavernous malformation (CCM)-associated genes: Krev interaction trapped 1 (KRIT1, also called CCM1), CCM2, and programmed cell death 10 (PDCD10, also called CCM3), which encode a heterotrimeric CCM protein complex affecting endothelium stabilization4,5. Here, CCM2 is linked to cerebral cavernous malformation.