How to manage a patient with microcytic hypochromic anemia?

Management of Microcytic Hypochromic Anemia

Start oral iron supplementation with ferrous sulfate 200 mg (65 mg elemental iron) three times daily immediately, and measure serum ferritin to confirm iron deficiency as the underlying cause. 1, 2

Immediate Diagnostic Workup

Your lab values show severe microcytosis (MCV 64.7 fL, normal 80-100), hypochromia (MCH 18.8 pg, MCHC 29.0 g/dL), and elevated RDW (17.2%), which strongly suggests iron deficiency anemia rather than thalassemia trait. 1, 2

Order these tests immediately:

• Serum ferritin is the single most specific test for iron deficiency, with levels <30 μg/L indicating low iron stores and <15 μg/L indicating absent stores, though a cutoff of 45 μg/L provides optimal sensitivity and specificity. 1, 2
• Transferrin saturation (TSAT) is more sensitive than hemoglobin alone for detecting iron deficiency, with TSAT <16% suggesting iron deficiency. 1, 2
• The elevated RDW (>14.0%) combined with low MCV strongly points toward iron deficiency rather than thalassemia trait, which typically presents with RDW ≤14.0%. 1

Treatment Protocol

Begin ferrous sulfate 200 mg (containing 65 mg elemental iron) three times daily for at least three months after hemoglobin normalizes to replenish iron stores. 1, 2, 3

• Add ascorbic acid (vitamin C) with each dose to enhance iron absorption. 1, 2
• If gastrointestinal side effects occur (nausea, constipation, dark stools), switch to ferrous gluconate or ferrous fumarate as alternatives. 1, 2
• Do not crush or chew tablets. 3
• A good response is defined as hemoglobin rise ≥10 g/L (≥1 g/dL) within 2 weeks, which confirms iron deficiency as the diagnosis. 1, 2

Expected Response and Monitoring

• Expect hemoglobin increase of at least 2 g/dL within 4 weeks of starting oral iron therapy. 2, 4
• Monitor hemoglobin concentration and red cell indices at three-monthly intervals for one year, then after a further year. 1, 2
• Provide additional oral iron if hemoglobin or MCV falls below normal during follow-up. 1, 2

Investigation of Underlying Cause

You must identify the source of iron loss in adults with confirmed iron deficiency. 2

• In premenopausal women, heavy menstrual bleeding is the most common cause. 2
• In men or non-menstruating women, investigate for gastrointestinal blood loss through history of melena, hematochezia, or occult bleeding. 2
• Consider gastrointestinal endoscopy if symptoms suggest GI pathology, as this may detect ulcers or malignancy. 2
• Screen for celiac disease if malabsorption is suspected based on dietary history or persistent symptoms. 2

Management of Treatment Failure

If the patient fails to respond to oral iron within 2-4 weeks, consider these possibilities:

• Non-compliance with medication regimen. 2
• Ongoing blood loss exceeding replacement capacity. 2
• Malabsorption disorders (celiac disease, H. pylori infection, autoimmune atrophic gastritis). 5, 2
• Switch to intravenous iron (iron sucrose or iron gluconate) if malabsorption is confirmed, with expected hemoglobin increase of at least 2 g/dL within 4 weeks. 2, 4

Differential Diagnosis Considerations

If ferritin is normal or elevated (>20 μg/L) despite microcytosis, consider genetic disorders of iron metabolism or heme synthesis rather than simple iron deficiency. 1, 2

• Order hemoglobin electrophoresis if microcytosis persists with normal iron studies or if MCV is disproportionately low relative to degree of anemia, to rule out thalassemia. 2
• Consider IRIDA (iron-refractory iron deficiency anemia) if there is remarkably low TSAT with low-to-normal ferritin and failure to respond to oral iron, though this typically presents in childhood. 5
• Genetic testing for disorders like SLC11A2, STEAP3, SLC25A38, or ALAS2 should be considered if extreme microcytosis (MCV <70) or family history of refractory anemia is present. 2

Critical Pitfalls to Avoid

• Do not assume all microcytic anemia is iron deficiency: anemia of chronic disease, thalassemia, and sideroblastic anemia must be differentiated to avoid unnecessary iron therapy. 2, 4
• Do not overlook combined deficiencies, as iron deficiency can coexist with B12 or folate deficiency. 2, 4
• In the presence of inflammation, ferritin levels up to 100 μg/L may still be consistent with iron deficiency, so add TSAT if ferritin is falsely elevated. 2
• Do not stop iron supplementation when hemoglobin normalizes—continue for at least three months to replenish iron stores. 1, 2