To study the incidence ofactive mycobacterial infections (aMI) in patients starting TNF αblockers, 262 patients were included in this study: 109 with rheumatoid arthritis(RA), 93 with ankylosing spondylitis (AS), 44 with juvenile idiopathic arthritis(JIA) and 16 with psoriatic arthritis (PsA). This evidence concerns the gene TNF and juvenile idiopathic arthritis.