What is the diagnosis and treatment for a patient with microcytic hypochromic anemia and elevated Red Cell Distribution Width?

Diagnosis and Treatment of Microcytic Hypochromic Anemia with Elevated RDW

Based on the laboratory values showing low MCH, low MCHC, and elevated RDW, iron deficiency anemia is the most likely diagnosis and should be treated with oral iron supplementation while investigating the underlying cause.

Laboratory Interpretation

• The patient's CBC shows microcytic (MCH: 25.6 L, MCHC: 31.3 L) anemia with an elevated RDW (15.8 H), which is highly suggestive of iron deficiency anemia 1
• The combination of microcytosis with elevated RDW is particularly characteristic of iron deficiency anemia, as the RDW increases earlier than other parameters in the development of iron deficiency 1, 2
• The elevated RBC count (6.10 H) and hematocrit (49.9 H) likely represent a compensatory response to maintain oxygen-carrying capacity despite reduced hemoglobin content in each cell 1

Diagnostic Approach

• Serum ferritin is the most sensitive test to confirm iron deficiency, with levels <12 μg/dL being diagnostic of iron deficiency 1
• Additional tests should include:
  • Transferrin saturation (should be <30% in iron deficiency) 1
  • Serum iron (typically low in iron deficiency) 1
  • Total iron binding capacity (increased in iron deficiency) 1
• Peripheral blood smear examination may reveal hypochromic microcytic cells with increased variation in size 3, 2

Differential Diagnosis

• The main differential diagnoses for microcytic hypochromic anemia include:

  • Iron deficiency anemia (elevated RDW) 1, 4
  • Thalassemia trait (typically normal RDW) 4
  • Anemia of chronic disease (variable RDW) 5
  • Sideroblastic anemia (variable presentation) 6

• The elevated RDW strongly favors iron deficiency over thalassemia trait, as demonstrated by the Green and King Index and RDW Index which have sensitivities of 90% for distinguishing these conditions 4

Underlying Causes to Investigate

• Gastrointestinal blood loss is the most common cause in adult men and post-menopausal women 1
  • Common GI causes include colonic cancer/polyps, NSAID use, gastric cancer, angiodysplasia, and inflammatory bowel disease 1
• In pre-menopausal women, menstrual blood loss is the most common cause 1
• Malabsorption conditions, particularly celiac disease, should be considered 1
• Poor dietary intake of iron is another potential cause 1

Treatment Recommendations

• Oral iron supplementation is the first-line treatment for iron deficiency anemia, typically given as ferrous sulfate 325 mg (65 mg elemental iron) 1-3 times daily between meals 1, 3
• A therapeutic response to three weeks of oral iron therapy (increase in hemoglobin and reduction in RDW) confirms the diagnosis of iron deficiency 1, 2
• For patients with inflammatory conditions, higher doses of iron may be needed 1
• In cases of malabsorption or intolerance to oral iron, intravenous iron may be necessary 1, 3
• Treatment should continue for 3-6 months after normalization of hemoglobin to replenish iron stores 1

Monitoring and Follow-up

• Monitor hemoglobin, MCV, and RDW to assess response to treatment 1
• Expect to see improvement in RDW within 1-2 weeks of starting iron therapy, followed by improvement in hemoglobin 2
• If no response to iron therapy after 4 weeks, reassess diagnosis and adherence 1
• Investigate and treat the underlying cause of iron deficiency to prevent recurrence 1, 3

Pitfalls and Caveats

• Not all patients with iron deficiency have elevated RDW, especially in early stages 1
• Combined deficiencies (iron plus B12 or folate) may mask typical findings 1
• Anemia of chronic disease can also present with microcytosis and may coexist with iron deficiency 1, 5
• Genetic disorders of iron metabolism (such as those described in the guidelines) are rare causes of microcytic anemia but should be considered if standard treatment fails 6