It is required that actual severity is determined comprehensively based on the presence/absence of systemic symptoms, such as fever and extraintestinal manifestations, abdominal findings (degree of abdominal pain, presence/absence of inflammatory masses and rebound tenderness), depth of ulceration, presence/absence of intestinal complications (hemorrhage, stenosis, fistulas), inflammatory response (CRP, white blood cell count, erythrocyte sedimentation rate), and degree of anemia [2]. The gene discussed is CRP; the disease is anemia (phenotype).