What is the diagnosis and treatment plan for a patient with microcytic, hypochromic anemia?

Diagnosis and Treatment of Microcytic Hypochromic Anemia in a 54-Year-Old Patient

Diagnosis

This patient has microcytic hypochromic anemia (Hb 9.4 g/dL, MCV calculated ~81 fL, MCH 24.5 pg, MCHC 30.1 g/dL) with an elevated RDW of 15.8%, which strongly suggests iron deficiency anemia as the primary diagnosis. 1

Diagnostic Algorithm

Step 1: Confirm Iron Deficiency

• Measure serum ferritin immediately—this is the most specific test for iron deficiency 2, 1
• Ferritin <15 μg/L confirms absent iron stores (specificity 0.99) 2
• Ferritin <30 μg/L indicates low body iron stores 2, 1
• Ferritin <45 μg/L provides optimal sensitivity/specificity trade-off in practice 2, 1
• Measure transferrin saturation (TSAT) as it is more sensitive than hemoglobin alone for detecting iron deficiency 1

Step 2: Rule Out Alternative Diagnoses

• The elevated RDW >14.0% with low MCV strongly favors iron deficiency over thalassemia trait (which typically has RDW ≤14.0%) 1, 3
• If ferritin is normal or elevated (>45 μg/L), measure serum iron and TSAT to exclude genetic disorders of iron metabolism 2, 1, 4
• Critical pitfall: Do not assume all microcytic anemia is iron deficiency—anemia of chronic disease, thalassemia, and sideroblastic anemia must be differentiated 1

Step 3: Identify the Source of Iron Loss

• Investigate for gastrointestinal blood loss (melena, hematochezia, occult bleeding) as this is the most common cause in adults 1
• Consider malabsorption disorders including celiac disease if dietary history suggests inadequate intake 1
• In men and non-menstruating women with confirmed iron deficiency, gastrointestinal investigation is warranted even with mild anemia 2

Treatment Plan

First-line treatment is oral ferrous sulfate 324 mg (65 mg elemental iron) two to three times daily for at least three months after correction of anemia to replenish iron stores. 1, 5

Treatment Algorithm

Initial Therapy

• Start ferrous sulfate 200 mg three times daily (equivalent to 65 mg elemental iron per dose) 1
• Do not crush or chew tablets 5
• Add ascorbic acid (vitamin C) to enhance iron absorption 1
• Alternative formulations if ferrous sulfate is not tolerated: ferrous gluconate or ferrous fumarate 1

Expected Response

• A good response is defined as hemoglobin rise ≥10 g/L (≥1 g/dL) within 2 weeks, confirming iron deficiency 1
• Expect hemoglobin increase of at least 2 g/dL within 4 weeks of starting treatment 1
• Continue oral iron for at least 3 months after anemia correction to replenish iron stores 1, 6

If Patient Fails to Respond to Oral Iron

• Consider intravenous iron if malabsorption is present (expect Hb increase ≥2 g/dL within 4 weeks) 1
• Evaluate for other causes of microcytic anemia including genetic disorders of iron metabolism or heme synthesis 1
• Test for thalassemia if RDW normalizes or remains near normal 1
• Critical consideration: If ferritin is low-normal (>20 mg/L) with low TSAT, or if there is family history of refractory anemia, suspect genetic disorders such as iron-refractory iron deficiency anemia (IRIDA) 1, 4

Monitoring Protocol

During Treatment

• Check hemoglobin and hematocrit at 2 weeks to confirm response 1
• Monitor hemoglobin concentration and red cell indices at 3-monthly intervals for one year, then after a further year 1
• Check serum ferritin and transferrin saturation to assess iron store repletion 1
• Provide additional oral iron if hemoglobin or MCV falls below normal 1

Common Pitfalls to Avoid

• Do not overlook combined deficiencies (iron deficiency coexisting with B12 or folate deficiency) 1
• Do not start empiric oral iron therapy when ferritin is elevated, as this could worsen iron overload in sideroblastic anemia or genetic disorders 4
• Serum ferritin may be falsely elevated in inflammatory conditions despite concurrent iron deficiency (ferritin is an acute phase protein) 2, 7
• In the presence of chronic inflammation, an SF cut-off of 45 μg/L provides better diagnostic accuracy 2