Rheumatoid arthritis is an autoimmune disease. It is characterized by autoantibodies against homocitrulline and citrulline. The autoantibodies that are positive in case of rheumatoid arthritis are: - Anti-perinuclear factors - Rheumatic factors - Anti-keratin antibodies - Anti-filaggrin antibodies Reference: https://academic.oup.com/rheumatology/article/41/7/809/1788313#:~:text=Rheumatoid%20arthritis%20(RA)%20has%20been,recently%20%5B2%2C%203%5D. Image via: https://www.orthobullets.com/basic-science/9085/rheumatoid-arthritis