Compared to the patients with normal serum IgG4, significantly (P < 0.05) more patients in the group with elevated serum IgG4 were male, had elevated IgE, AST ≥ 10 ULN, ALT ≥ 10 ULN, decreased C4, concomitant allergic disease, and constipation. Here, C4A is linked to allergic disease.