A comparison of 19 AIH patients with elevated serum IgG4 with 20 cases of AIH with normal serum IgG4 revealed that male patients and those with elevated IgE, AST ≥ 10 ULN, ALT ≥ 10 ULN, reduced C4, allergic disease, or constipation were more commonly seen in the AIH group with elevated serum IgG4. This evidence concerns the gene C4A and allergic disease.