How do you approach a patient with fatigue, pallor, low hemoglobin (Hb) level, and microcytic anemia?

Approach to a 30-Year-Old Woman with Microcytic Anemia

The most appropriate approach for this 30-year-old woman with fatigue, pallor, Hb 9 g/dL, and MCV 70 fL is to begin with iron studies, as iron deficiency anemia is the most likely diagnosis requiring prompt iron supplementation. 1

Initial Assessment of Microcytic Anemia

Laboratory Evaluation

• Confirm microcytic anemia with peripheral blood smear to assess RBC morphology 1
• Order iron studies including:
  • Serum ferritin
  • Serum iron
  • Total iron binding capacity (TIBC)
  • Transferrin saturation 1
• Consider reticulocyte count to assess bone marrow response 1
• If iron studies are inconclusive, consider free erythrocyte protoporphyrin level 2

Differential Diagnosis for Microcytic Anemia (MCV < 80 fL)

• Iron deficiency anemia (most common cause) 3, 4
• Thalassemia trait 1, 5
• Anemia of chronic disease 1
• Sideroblastic anemia 1
• Lead toxicity (especially in children) 2

Diagnostic Algorithm

Step 1: Iron Studies Interpretation

• Low ferritin (< 30 ng/mL), low serum iron, high TIBC, and transferrin saturation < 15% confirms iron deficiency anemia 1, 3
• Normal/high ferritin with low serum iron suggests anemia of chronic disease 1
• Normal/high ferritin with normal/high serum iron suggests thalassemia trait 5, 2

Step 2: If Iron Deficiency is Confirmed

• Investigate underlying cause of iron deficiency:
  • Menstrual blood loss (common in women of reproductive age) 3
  • Gastrointestinal blood loss (especially if no obvious source of blood loss) 3
  • Malabsorption disorders 3
  • Pregnancy or recent pregnancy 3, 6
  • Poor dietary intake 3

Step 3: If Iron Studies Do Not Confirm Iron Deficiency

• Consider hemoglobin electrophoresis to evaluate for thalassemia 1, 5
• Evaluate for chronic diseases that may cause anemia 1
• Consider bone marrow examination if diagnosis remains unclear 1

Treatment Approach

For Iron Deficiency Anemia

• Oral iron supplementation (first-line therapy):
  • Ferrous sulfate 325 mg (65 mg elemental iron) 1-3 times daily 3
  • Continue treatment for 3-6 months after hemoglobin normalizes to replenish iron stores 3
• Monitor response with repeat hemoglobin after 4-8 weeks 3
• If no response to oral iron, consider:
  • Compliance issues
  • Ongoing blood loss
  • Malabsorption
  • Incorrect diagnosis 3
• Consider parenteral iron if oral iron is not tolerated or ineffective 3

For Thalassemia Trait

• Usually no specific treatment required 5
• Avoid unnecessary iron supplementation 5
• Genetic counseling may be appropriate 1

Common Pitfalls to Avoid

• Failing to investigate the underlying cause of iron deficiency, especially in adults 3
• Misdiagnosing thalassemia trait as iron deficiency, leading to unnecessary iron supplementation 5
• Overlooking combined deficiencies (e.g., iron deficiency with folate deficiency) 6
• Assuming all microcytic anemias are due to iron deficiency without appropriate testing 2
• Discontinuing iron therapy too soon before replenishing iron stores 3

By following this systematic approach, the underlying cause of this patient's microcytic anemia can be identified and appropriate treatment initiated to address both the anemia and its root cause.