By searching the literature, we discovered 13 modifier genes with a variety of functions, including antioxidant and cellular stress genes such as catalase and SOD2. Genes involved in mineralization and calcium metabolism pathways, such as XYLT1/2, MGP, and MMP2, genes involved in the breakdown of ATP, such as ENPP1, and genes involved in angiogenesis, such as VEGFA. Another modifier gene, SPP1, may also be associated with PXE. The gene discussed is MMP2; the disease is Pseudoxanthoma elasticum.