What is the diagnosis and treatment for a patient with microcytic, hypochromic anemia (RBC 6.88, MCV 61, MCH 17.2, MCHC 28.2, RDW 19.7)?

Microcytic Hypochromic Anemia: Diagnosis and Management

Primary Diagnosis

This presentation is most consistent with iron deficiency anemia (IDA), given the severely elevated RDW (19.7) combined with marked microcytosis (MCV 61), which strongly distinguishes IDA from thalassemia trait. 1, 2

The combination of low MCV with RDW >14.0% is the key discriminating feature—thalassemia minor typically presents with RDW ≤14.0%, while your RDW of 19.7 definitively points toward iron deficiency. 1

Immediate Diagnostic Workup

Confirm the diagnosis with serum ferritin as the single most useful test:

• Ferritin <15 μg/L indicates absent iron stores 1
• Ferritin <30 μg/L indicates low body iron stores 1
• A cutoff of 45 μg/L provides optimal sensitivity and specificity for iron deficiency 1, 2
• If ferritin is falsely elevated due to inflammation, add transferrin saturation (TSAT <16% suggests iron deficiency) 1

The extremely low MCV (61) warrants consideration of genetic disorders if iron studies are normal or near-normal, particularly if there is family history of refractory anemia or extreme microcytosis (MCV <70). 3

First-Line Treatment Protocol

Start oral ferrous sulfate 324 mg (65 mg elemental iron) two to three times daily:

• Do not crush or chew tablets 4
• Continue for at least three months after hemoglobin normalizes to fully replenish iron stores 1, 2
• Add ascorbic acid (vitamin C) 200-500 mg with each dose to enhance absorption 2

Alternative formulations if gastrointestinal side effects occur:

• Ferrous gluconate or ferrous fumarate 1, 2

Expected Response and Monitoring

Hemoglobin should rise ≥1 g/dL (≥10 g/L) within 2 weeks, confirming iron deficiency as the cause. 1, 2

Monitor at these intervals:

• Check hemoglobin, hematocrit, MCV, and MCH at 2 weeks 2
• Recheck at 4 weeks (expect ≥2 g/dL increase) 1, 2
• Monitor at 3 months, then every 3 months for the first year 1, 2
• Annual monitoring thereafter 2

Mandatory Investigation for Underlying Cause

You must identify the source of iron loss—iron deficiency anemia in adults always requires explanation:

For non-menstruating women or men:

• Fast-track gastrointestinal referral is warranted for hemoglobin <10 g/dL to exclude malignancy 1, 2
• Investigate for gastrointestinal blood loss (melena, hematochezia, occult bleeding) 1

For menstruating women:

• Assess menstrual blood loss patterns 2
• Still consider GI evaluation if symptoms present 1

Additional investigations:

• Screen for celiac disease if malabsorption suspected 1
• Evaluate dietary intake 2

When to Escalate to Intravenous Iron

Consider IV iron if any of the following apply:

• Documented malabsorption 1, 2
• Patient cannot tolerate oral iron despite trying alternative formulations 2
• Ongoing blood loss exceeds oral replacement capacity 2
• No hemoglobin response after 4 weeks of adequate oral therapy 2
• Expected hemoglobin increase with IV iron is at least 2 g/dL within 4 weeks 1, 2

Critical Differential Diagnosis Considerations

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

• Non-compliance with therapy 1
• Ongoing blood loss 1
• Malabsorption 1
• Genetic disorders of iron metabolism (IRIDA—requires IV iron as oral is ineffective) 1

If iron studies are normal or near-normal with this degree of microcytosis:

• Order hemoglobin electrophoresis to evaluate for thalassemia 1
• Consider genetic testing for disorders like SLC11A2, STEAP3, SLC25A38, ALAS2, or ABCB7 if extreme microcytosis (MCV <70) or family history present 3
• Bone marrow examination may be needed to look for ring sideroblasts if ferritin is normal/high with abnormal iron studies 3

Common 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. 1
• Do not overlook combined deficiencies—iron deficiency can coexist with B12 or folate deficiency. 1
• Do not stop iron therapy when hemoglobin normalizes—continue for 3 months to replenish stores. 1, 2
• In the presence of inflammation, ferritin up to 100 μg/L may still be consistent with iron deficiency—add TSAT in these cases. 1