From the Guidelines
Anemia in Crohn's disease is primarily caused by a combination of chronic inflammation, intestinal blood loss, and nutrient malabsorption, with the most common type being anemia of chronic disease, followed by iron deficiency anemia. The causes of anemia in Crohn's disease are multifactorial, including:
- Chronic inflammation leading to anemia of chronic disease, as inflammatory cytokines disrupt iron metabolism and reduce red blood cell production 1
- Intestinal blood loss due to inflamed intestinal mucosa and ulcerations, resulting in iron deficiency anemia 1
- Malabsorption of essential nutrients like vitamin B12 and folate, particularly when Crohn's affects the terminal ileum where B12 absorption occurs 1
- Medication side effects, such as sulfasalazine interfering with folate absorption and azathioprine or 6-mercaptopurine suppressing bone marrow function 1
- Hemolytic anemia due to autoimmune processes or medication reactions
- Chronic kidney disease associated with long-standing Crohn's, reducing erythropoietin production and contributing to anemia
According to the most recent and highest quality study, IV iron is recommended as the first-line treatment for iron deficiency anemia in patients with Crohn's disease, especially those with active disease or previous intolerance to oral iron 1. Regular monitoring of complete blood counts and iron studies is essential for early detection and management of anemia in Crohn's disease patients. The European Crohn's and Colitis Organization recommends IV iron over oral iron as first-line therapy for patients with a hemoglobin level <10 g/dL, while oral iron may be appropriate in carefully selected patients with mild anemia and clinically inactive disease 1.
Key points to consider in the management of anemia in Crohn's disease include:
- Assessing the presence of anemia in all patients with Crohn's disease, regardless of age 1
- Using complete blood count, serum ferritin, and C-reactive protein for laboratory screening 1
- Initiating iron supplementation in all patients with iron-deficiency anemia, and considering IV iron as the first-line treatment 1
- Monitoring patients regularly to assess response to treatment and adjust therapy as needed 1
From the Research
Causes of Anemia in Crohn's Disease
The causes of anemia in Crohn's disease are multifactorial, including:
- Absolute iron deficiency (iron deficiency anemia) 2, 3, 4, 5
- Functional iron deficiency (inflammation anemia or anemia of chronic disease) 2, 3, 5
- Folic acid or vitamin B12 deficiency 2, 4
- Adverse effects from medications (salicylic derivatives and immunosuppressive drugs) 2
- Chronic blood loss by mucosal ulcerations 3
- Malabsorption (including duodenal involvement and surgical removal) 3
- Inadequate intake 3
Relationship Between Crohn's Disease Activity and Anemia
There is a correlation between the degree of Crohn's disease activity and the severity of anemia:
- The Crohn's Disease Activity Index (CDAI) and C-reactive protein level correlate with the severity of anemia 2
- Disease activity is determining the degree of anemia in Crohn's disease 4
- Impaired intestinal iron absorption in Crohn's disease correlates with disease activity and markers of inflammation 6
Iron Deficiency and Supplementation
Iron deficiency is a common underlying condition in anemia associated with Crohn's disease:
- Oral iron supplementation seems effective for short periods but intolerance leads to discontinuation in up to 21% of patients 4
- Intravenous iron supplementation is safe, effective, and does not carry the same hazards as oral iron supplementation 4, 5
- Iron deficiency and iron supplementation have been associated with alterations to gut microbiota 3