The first approach to find common genetic risk factors was conducted in a case-control study with Danish white adults, documenting that frequencies of IL-1A -889 and +4845, and IL-1B -511 and +3954 genotypes were similar among localized and generalized aggressive periodontitis (LAgP and GAgP), juvenile idiopathic arthritis, RA, and healthy control groups [19]. Here, IL1A is linked to rheumatoid arthritis.