FGF2 and juvenile idiopathic arthritis: The average level of bFGF significantly increased in children with an age of JIA onset from 15 to 18 years versus an age of JIA onset up to 3 years (p = 0.003), 3–5 years (p = 0.025), and 11–14 years (p = 0.001) and in children with an age of JIA onset from 6 to 10 years versus an age of JIA onset from 11–14 years (p = 0.041).