Introduction
endometriosis, SpA, tumor necrosis, TNF-α, gynecological disease, spondyloarthritis, autoimmune imbalance
INFLAMMATORY ARTHRITIS, ENDOMETRIOSIS, TUMOR NECROSIS, GYNECOLOGICAL DISEASE, ANKYLOSING SPONDYLITIS, DISEASE, DISEASES, INFLAMMATION, SPONDYLOARTHRITIS, CAVITY, PATHOGENESIS, ENDOTHELIAL DYSFUNCTION
Ankylosing spondylitis (AS) is a long-term inflammatory arthritis caused by autoimmune imbalance, affiliated to the spondyloarthritis (SpA). Its pathogenesis is related to immunological abnormalities involving tumor necrosis factor-α (TNF-α) and T helper17 cells. With the increasing understanding of the disease, gender problem of clinical is an increasing topical issue, the ratio of male to female in AS patients has been increased from 5:1 to 2:1 in a recent study, and 1:1 for nr-axSpAEndometriosis is a familiar benign gynecological disease in which endometrial cells are active outside the uterine cavity. The increased levels of T helper17 cells subsets and TNF-α factor may provide an inflammatory environment for the occurrence and development of endometriosisPossible reasons for the association between endometriosis and an increased risk of developing AS are as follows: first, AS and endometriosis both have a strong genetic predisposition. Second, the two diseases may share various co-occurring genetic backgrounds. For example, there are variations in the expression levels of various genes associated with inflammation, angiogenesis, endothelial dysfunction, and immune disordersMendelian randomization (MR) uses instrumental variables (IVs) in the analysis of genetic variation, to identify whether exposures and outcomes were observed and consistent with causal effects, avoiding potential confounders because genetic variants were randomly assignedTherefore, the present study was designed to assess the causal effect of endometriosis in multiple clinical states on AS using multiple MR methods.