Grijalva analyzed whether initiation of TNF-α antagonists compared with nonbiologic drugs was associated with an increased risk of serious infections in a cohort of patients affected by rheumatoid arthritis, inflammatory bowel disease, psoriasis, psoriatic arthritis, or ankylosing spondylitis; rates were 5.41 for TNF-α antagonists and 5.37 for traditional systemic drugs per 100 person-year, showing no significant difference between the 2 groups [39]. This evidence concerns the gene TNF and psoriatic arthritis.