What is the diagnosis and treatment for a patient with microcytic anemia and lab results indicating low MCV and MCH?

Diagnosis and Treatment of Microcytic Anemia

Based on the laboratory values (MCV 65, MCH 18, MCHC 27.7), this patient has iron deficiency anemia and should be treated with oral ferrous sulfate 200 mg three times daily for 3 months after hemoglobin normalization. 1

Diagnosis

The patient's lab results clearly indicate microcytic hypochromic anemia:

• Hemoglobin: 13.8 g/dL (mildly decreased)
• MCV: 65 fL (significantly decreased, normal >80 fL)
• MCH: 18 pg (decreased, normal >27 pg)
• MCHC: 27.7 g/dL (decreased, normal >32 g/dL)
• RDW: 18.4% (elevated, indicating variation in red cell size)

These findings are most consistent with iron deficiency anemia, which is the most common cause of microcytic anemia 2, 3. The extremely low MCV (65) with low MCH and MCHC values are characteristic of iron deficiency.

Differential Diagnosis

While iron deficiency is most likely, other causes of microcytic anemia to consider include:

1. Thalassemia trait - typically has very low MCV but normal or high RBC count
2. Anemia of chronic disease - usually less microcytic (MCV 70-80)
3. Lead toxicity - rare but possible cause
4. Sideroblastic anemia - uncommon cause 3, 4

Diagnostic Workup

To confirm the diagnosis:

1. Serum ferritin - This is the best single laboratory test for diagnosing iron deficiency 5

   • <15 μg/L confirms iron deficiency
   • 15-45 μg/L suggests possible iron deficiency 1

2. Additional iron studies if ferritin is not clearly low:

   • Serum iron
   • Total iron binding capacity (TIBC)
   • Transferrin saturation 1, 3

3. If iron deficiency is confirmed, investigate the underlying cause:

   • In adults, iron deficiency is presumed to be from blood loss, most commonly gastrointestinal 3
   • Consider GI malignancy, especially in older adults
   • In women, consider heavy menstrual bleeding

Treatment

First-line Treatment

• Oral iron supplementation: Ferrous sulfate 324 mg (65 mg elemental iron) three times daily 1, 6
• Continue therapy for 3 months after hemoglobin normalizes to replenish iron stores 1
• Monitor response with repeat CBC in 2-4 weeks 1
• Target hemoglobin rise of ≥10 g/L within 2 weeks indicates good response 1

Alternative Treatments

• If oral iron is not tolerated or ineffective, consider intravenous iron 1
• IV iron is indicated when:
  • Oral therapy fails
  • Patient cannot tolerate oral iron (GI side effects)
  • Patient has malabsorption
  • Iron losses exceed what can be replaced orally 2

Monitoring and Follow-up

• Repeat CBC in 2-4 weeks to assess response 1
• Monitor ferritin and transferrin saturation monthly 1
• Continue iron therapy for 3 months after hemoglobin normalizes 1

Common Pitfalls to Avoid

• Failing to investigate underlying cause of iron deficiency, especially in adults 1, 3
• Relying solely on MCV or MCH without confirming iron status 1
• Misinterpreting ferritin levels in inflammatory states (ferritin can be falsely elevated) 1
• Not taking oral iron properly:
  • Should be taken on empty stomach if possible
  • Avoid taking within 2 hours of tetracycline antibiotics 6
  • Anticipate and manage side effects like constipation, nausea, and GI discomfort 6

Special Considerations

• If thalassemia is suspected (very low MCV with normal RBC count), hemoglobin electrophoresis should be performed 3
• In pregnant women, iron requirements are higher and may need increased supplementation 1
• In patients with inflammatory bowel disease, IV iron may be more effective than oral iron 1