Additionally, the differences in P2X3 expression score between women with and without pain reached statistical significance for ovarian endometriosis (P = 0.000), peritoneal endometriosis (P = 0.000) and deeply infiltrating endometriosis (P = 0.000), respectively, but no significant differences of P2X3 expression frequency in ovarian endometriosis, peritoneal endometriosis or deeply infiltrating endometriosis between women with and without pain were found (Table 3). This evidence concerns the gene P2RX3 and ovarian endometriosis.