Somatic mutations in CCM genes (CCM1/KRIT1, CCM2/MGC4607, and CCM3/PDCD10) were reported early in simplex CCM lesions (12), and recent studies reported that over one-third of simplex CCMs contain the MAP3K3 (c.1323C>G [p. Ile441Met]) somatic mutation (13, 14); the MAP3K3 and CCM gene mutations were mutually exclusive (13). The gene discussed is MAP3K3; the disease is cerebral cavernous malformation.