Alternative relapsing and remitting inflammation in intestinal mucosa are frequently present in IBD patients, and considerable amount of proinflammatory factors (e.g., TNF-α, IFN-γ, IL-6, and IL-17) in intestinal microenvironment plays important roles in impairing iron absorption and erythropoietin production in response to anemia. The gene discussed is IFNG; the disease is anemia (phenotype).