How to manage a patient with microcytic anemia and low ferritin?

Management of Microcytic Anemia with Low Ferritin

Oral iron supplementation with 35-65 mg of elemental iron daily is the recommended first-line treatment for this patient with microcytic anemia (MCV 78) and low ferritin (43). 1

Diagnosis Confirmation

The laboratory values presented (ferritin 43, MCV 78, RDW 12.7, microcytosis 1+) are consistent with iron deficiency anemia, which is the most common cause of microcytic anemia 2. While the ferritin level of 43 μg/L is not severely low, it is below the optimal level, especially considering that:

• Serum ferritin <30 μg/L definitively indicates absent iron stores 1
• Values between 30-100 μg/L may still represent iron deficiency, particularly in the presence of microcytosis

The normal RDW (12.7%) is somewhat atypical for iron deficiency, which usually presents with elevated RDW (>14%) 1. This requires consideration of other causes of microcytic anemia:

Parameter	Iron Deficiency	Thalassemia Trait	Anemia of Chronic Disease
MCV	Low	Very low (<70 fl)	Low/Normal
RDW	High (>14%)	Normal (≤14%)	Normal/Slightly elevated
Ferritin	Low (<30 μg/L)	Normal	Normal/High

Treatment Plan

1. Initiate oral iron supplementation:

   • Ferrous sulfate 324 mg (65 mg elemental iron) once daily 3
   • Take on empty stomach with vitamin C to enhance absorption
   • Avoid tea, coffee, calcium, and antacids within 2 hours of iron intake 1

2. Duration of treatment:

   • Continue for 3 months after hemoglobin normalizes to replenish iron stores 1
   • Monitor hemoglobin response after 4 weeks of treatment

3. Further evaluation:

   • Investigate underlying cause of iron deficiency
   • For adults, iron deficiency is presumed to be caused by blood loss 2
   • Stool guaiac test for occult blood is recommended 1
   • Consider gastrointestinal evaluation, especially if patient is >50 years old 4

Special Considerations

• Differential diagnosis: If no improvement after 4 weeks of iron therapy, consider:

  • Thalassemia trait (normal ferritin, normal RDW, MCV often <70)
  • Anemia of chronic disease (normal/high ferritin, low iron, low TIBC)
  • Sideroblastic anemia (requires bone marrow examination) 5
  • Aceruloplasminemia (rare, presents with high ferritin) 6

• Common pitfalls to avoid:

  • Inadequate duration of iron replacement 1
  • Attributing iron deficiency solely to menstrual loss without proper GI investigation 1
  • Failing to evaluate for other nutrient deficiencies if anemia persists 1
  • Not considering rare causes like thalassemia in patients with particularly low MCV 7

• Follow-up:

  • Check hemoglobin after 4 weeks of treatment
  • If no increase of 1-2 g/dL in hemoglobin, consider:
    • Non-compliance
    • Malabsorption
    • Continued bleeding
    • Incorrect diagnosis 4

Iron deficiency anemia requires both correction of the deficiency and identification of the underlying cause to prevent recurrence and ensure optimal patient outcomes.