PIK3CA and erythema multiforme: Recent research proposing genetic and epigenetic changes as a cause of EM, such as genetic mutations in KRAS, ARID1A, PI3Ka, PIK3ca, ARHGAP35, PP2A in eutopic and ectopic endometrium [55] also support the secretome theory, as the reported genes affect processes driven by the uterine secretome, such as implantation, cell invasion and migration (KRAS [56], ARID1A [57], PI3Ka [58], PIK3ca [59], ARHGAP35 [60], PP2A [61]).