These processes are related to changes in several important cell signaling pathways, including VEGF/VEGFR, Notch, β-adrenaline, Tie2/angiopoietins, PI3K/AKT/mTOR, HIF-α-mediated PDGF/ PDGF-R -β pathway.[24] However, the exact mechanism of IH pathogenesis is unclear. This evidence concerns the gene AKT1 and isolated hemihyperplasia.