Specifically, clinical trials using PUVA have demonstrated the ability of photoactivated psoralen to downregulate the expression of vascular endothelial growth factor (VEGF), a protein known to stimulate the formation of blood vessels through tyrosine kinase pathways, and result in an aberrant formation of these vascular malformations in various diseases (Bethea et al. 1999; Longuet-Perret et al. 1998). This evidence concerns the gene VEGFA and vascular malformation.