ERAP1 and psoriasis: After removing 135 duplicate articles, the remaining 51 articles were subjected to screening by title and abstracts; after removing 7 articles irrelevant to ERAP1 and 19 reviews and letters, there were 25 articles that were eligible for full-text review; after excluding 5 article studies with insufficient data and 11 articles with irrelevant data, 9 original case-control studies consisting of 4858 psoriasis cases and 10542 healthy controls were finally included.