Multiple bilateral renal cysts are characteristic of polycystic kidney disease (PKD), and its pathology has been linked to over-activation of Hypoxia-inducible factor 1-alpha (HIF-1α) in the epithelial layer and Hypoxia-inducible factor 2-alpha (HIF-2α) in the cystic wall [16]. The gene discussed is EPAS1; the disease is cystic kidney disease.