When patient background and clinical parameters at diagnosis were compared between patients with severe and non-severe (mild and moderate) AIH, Alb (2.7 vs. 3.5 g/dl, p < 0.05) and PT (46.4 vs. 81.3 %, p < 0.005) were significantly lower in the severe AIH group, and serum IL-21 (396.7 vs. 264.7 pg/ml, p < 0.05) and IL-18 (1776.6 vs. 808.6 pg/dl, p < 0.05) were significantly higher in the severe AIH group. This evidence concerns the gene IL18 and autoimmune hepatitis.