Numerous innovative biomarkers identified in cases of endometriosis and infertility have been studied over the past years, including micro-RNAs, BCL6 endometrial expression, cytotoxic T-lymphocyte antigen 4, human leukocyte antigen G, programmed cell death protein 1, programmed cell death ligand 1 immune checkpoint molecules, plasma fibronectin-fibrin complexes, homeobox A10 gene, systemic inflammatory response markers, uterine natural killer cells, and the eutopic endometrium proteome. The gene discussed is PDCD1; the disease is endometriosis.