Microcytic Hypochromic Anemia: Iron Deficiency Anemia
This patient has iron deficiency anemia (IDA) requiring oral iron supplementation as first-line treatment, with a goal to normalize hemoglobin levels and iron stores. 1
Diagnosis
The laboratory findings definitively indicate microcytic hypochromic anemia:
- Low hemoglobin (11.3-11.8 g/dL, reference 11.7-15.5 g/dL) 1
- Low MCH (25.1-25.7 pg, reference 27.0-33.0 pg) indicating hypochromia 1
- Low MCHC (30.3-31.1 g/dL, reference 31.6-35.4 g/dL) confirming hypochromia 1
- Low-normal MCV (81.9-83.1 fL) indicating microcytosis 1
- Normal white blood cell and platelet counts excluding primary bone marrow disorders 1
Iron deficiency is the most likely diagnosis given the microcytic hypochromic pattern with normal inflammatory markers. 1
Essential Diagnostic Workup
Immediately order these iron studies to confirm the diagnosis:
- Serum ferritin: A level <12-15 μg/L is diagnostic of absolute iron deficiency 1
- Transferrin saturation (TSAT): A level <16-20% indicates iron deficiency 1
- Serum iron and total iron binding capacity (TIBC) 1
Critical interpretation points:
- If ferritin <30 μg/L with TSAT <20%, this confirms iron deficiency anemia 1
- If ferritin is 30-100 μg/L with TSAT <16%, consider combined iron deficiency and anemia of chronic disease 1
- If ferritin >100 μg/L with TSAT <20%, anemia of chronic disease with functional iron deficiency is likely 1
Additional testing to identify the underlying cause:
- Stool guaiac test for occult gastrointestinal bleeding 1
- Upper endoscopy with small bowel biopsy to exclude celiac disease and gastric pathology 1
- Colonoscopy or barium enema to exclude colonic malignancy in adults 1
- Menstrual history in premenopausal women 1
Treatment Algorithm
First-line treatment: Oral iron supplementation 1
- Dosing: 100-200 mg elemental iron daily 1
- Alternative regimen: Intermittent dosing (every other day or three times weekly) is as effective with fewer side effects 2
- Goal: Normalize hemoglobin levels and replenish iron stores 1
Expected response:
- Hemoglobin should increase by at least 2 g/dL within 4 weeks of treatment 1
- Continue iron supplementation for 3-6 months after hemoglobin normalization to replenish iron stores 1
Second-line treatment: Intravenous iron 1
Indications for IV iron include:
- Intolerance to oral iron (nausea, constipation, diarrhea) 1
- Malabsorption (celiac disease, inflammatory bowel disease) 1
- Failure to respond to oral iron after 4 weeks 1
- Severe anemia requiring rapid correction 1
Monitoring during treatment:
- Recheck hemoglobin in 4 weeks to assess response 1
- Recheck iron studies after hemoglobin normalization to confirm iron store repletion 1
- Long-term monitoring every 6-12 months if the underlying cause persists 1
Critical Pitfalls to Avoid
Do not assume normal hemoglobin excludes iron deficiency. Iron depletion can occur with normal hemoglobin, and measuring only CBC without iron studies will miss early iron deficiency. 3
Do not overlook gastrointestinal pathology. In adult men and postmenopausal women, iron deficiency anemia is caused by gastrointestinal blood loss until proven otherwise, and both upper and lower GI tract evaluation is mandatory to exclude malignancy. 1
Do not misinterpret ferritin in the presence of inflammation. Ferritin is an acute-phase reactant and can be falsely elevated in inflammatory conditions, infection, or malignancy. In these settings, ferritin <100 μg/L suggests coexistent iron deficiency. 1
Do not use intravenous iron as first-line therapy without attempting oral iron. Oral iron is effective for mild anemia (hemoglobin >10 g/dL) and should be tried first unless contraindications exist. 1
Do not stop iron supplementation when hemoglobin normalizes. Iron stores must be replenished, requiring continued supplementation for 3-6 months after hemoglobin correction. 1