MAPK3 and vascular malformation: KRAS activating mutations have been found to specifically activate the MAPK‐ERK signaling pathway in endothelial cells derived from arteriovenous malformations of the brain, indicated by the increased level of ERK1/2 phosphorylation in endothelial cells cultures with mutant KRAS. 11Moreover, a study from Al‐Olabi, et al. found that multiple mosaic‐activating variants in four genes including KRAS associated with the activated MAPK pathway would cause sporadic vascular malformations.12