CTLA4 and rheumatoid arthritis: This may reflect shared genetic susceptibility and immune pathways, as susceptibility genes for AITD such as forkhead box protein P3 (FOXP3) and cytotoxic T-lymphocyte protein 4 (CTLA-4) can affect central and peripheral immune tolerance, thereby increasing the risk of developing other autoimmune diseases, including rheumatoid arthritis and systemic lupus erythematosus (155).