In comparing children with JIA alone vs those with JIA-U (Table 1), more children with JIA-U had oligoarticular persistent JIA (75 % vs. 34 %, p < 0.001), were significantly younger at arthritis diagnosis (2.8 vs. 7.7 years, p < 0.001), ANA positive (55 % vs. 36 %, p = 0.017), rheumatoid factor negative (0 % vs. 11 %, p = 0.013) and anti-CCP negative (0 % vs. 10 %, p = 0.020). The gene discussed is BTG3; the disease is Arthritis.