What is the treatment for microcytic anemia?

Treatment of Microcytic Anemia

The treatment for microcytic anemia depends on the underlying cause, with oral iron supplementation (35-65 mg elemental iron daily) being the first-line therapy for iron deficiency anemia, which is the most common cause. 1

Diagnostic Approach to Guide Treatment

Before initiating treatment, it's essential to identify the specific type of microcytic anemia:

1. Laboratory Assessment:

   • Complete blood count with MCV (<80 fl in adults)
   • Iron studies: serum ferritin, iron, TIBC, transferrin saturation
   • RDW (elevated in iron deficiency)
   • Consider hemoglobin electrophoresis if thalassemia suspected

2. Differential Diagnosis:

   • Iron deficiency anemia (low ferritin <30 μg/L, high RDW >14%)
   • Thalassemia (very low MCV <70 fl, normal RDW, normal/high RBC count)
   • Anemia of chronic disease (normal/high ferritin, low TSAT)
   • Sideroblastic anemia (consider ALAS2, SLC25A38, STEAP3, ABCB7 defects) 2

Treatment by Cause

1. Iron Deficiency Anemia

• Oral Iron Therapy:

  • Ferrous sulfate 324 mg (65 mg elemental iron) 1-2 tablets daily 3
  • Continue for 3 months after hemoglobin normalizes to replenish stores 1
  • Take on empty stomach to maximize absorption

• Parenteral Iron:

  • Consider for patients with malabsorption, intolerance to oral iron, or ongoing blood loss exceeding oral replacement capacity 1
  • Options include iron sucrose, ferric carboxymaltose, or iron dextran

2. Genetic Disorders of Iron Metabolism or Heme Synthesis

• STEAP3 Defects:

  • Erythrocyte transfusions in combination with erythropoietin
  • Iron chelation therapy for systemic iron loading 2

• SLC25A38 Defects:

  • Hematopoietic stem cell transplantation (curative option)
  • Symptomatic treatment with erythrocyte transfusions and chelation therapy 2

• ABCB7 Defects:

  • Treatment of anemia generally not indicated (mild anemia) 2

• ALAS2 Defects (X-linked Sideroblastic Anemia):

  • Pyridoxine (vitamin B6) 50-200 mg daily initially
  • If responsive, maintain on 10-100 mg daily lifelong
  • Treat iron loading with phlebotomies 2

3. Thalassemia

• Treatment depends on severity:
  • Mild forms may require no specific treatment
  • Severe forms may require regular blood transfusions and iron chelation 4

Monitoring and Follow-up

• Monitor hemoglobin response after initiating treatment
• For iron deficiency, expect 1-2 g/dL increase in hemoglobin within one month of treatment 5
• If no improvement after one month of oral iron:
  • Consider malabsorption
  • Evaluate for ongoing blood loss
  • Consider alternative diagnoses 5

Common Pitfalls to Avoid

• Treating without identifying the underlying cause
• Inadequate duration of iron therapy (not continuing for 3 months after hemoglobin normalizes) 1
• Failing to investigate for gastrointestinal bleeding in men and postmenopausal women with iron deficiency 5
• Overlooking genetic causes in patients with refractory microcytic anemia 2
• Not considering functional iron deficiency in inflammatory conditions despite normal ferritin 1

Special Populations

• Pregnant women: Higher iron requirements; may need supplementation
• Elderly patients: Investigate for gastrointestinal malignancy (9% of those >65 years with iron deficiency anemia have GI cancer) 5
• Patients with heart failure: Require special consideration to prevent significant morbidity and mortality 4

Remember that serum ferritin is the most specific test for iron deficiency, with levels <15 μg/L indicating absent iron stores, though values up to 30 μg/L are still consistent with iron deficiency 1.