The high level of sfas in peritoneal fluid of EMs patients and the high expression of fasL in immune cells will increase the fas-mediated immune cell apoptosis in the abdominal cavity, reduce the immune scavenging activity, and protect the ectopic endometrium, and all of these contribute to the survival of ectopic cells and the genesis and development of EMs. The gene discussed is FASLG; the disease is eosinophilia-myalgia syndrome.