Initially considered a defining feature of sporadic CCM, where somatic activating mutations in PIK3CA occur in the absence of germline CCM gene defects, PIK3CA gain‐of‐function (GOF) mutations have now also been identified across all three genotypes of familial CCM (Hong et al. 2021; Weng et al. 2021). This evidence concerns the gene PIK3CA and cerebral cavernous malformation.