Several diseases have been reported to increase serum ADA activity in humans, including inflammation such as chronic tonsillitis, rhinosinusitis or otitis media [4], immune mediated disorders such as systemic lupus erythematosus [18, 19] or rheumatoid arthritis [20], and malignancies such as chronic lymphocytic leukemia [21], breast cancer [22] or bladder cancer [23]. Here, ADA is linked to rheumatoid arthritis.