What is the appropriate management for a patient with microcytic anemia?

Management of Microcytic Anemia in a 51-Year-Old Female

Begin with oral iron supplementation using ferrous sulfate 200 mg three times daily for at least three months after hemoglobin correction, as this patient's laboratory values (MCV 75.7 fL, MCH 24.4 pg, elevated RDW 15.6) strongly suggest iron deficiency anemia. 1, 2

Diagnostic Confirmation

Before initiating treatment, obtain the following iron studies to confirm the diagnosis:

• Serum ferritin is the most specific single test for iron deficiency, with levels <15 μg/L indicating absent iron stores and <30 μg/L indicating low body iron stores 1, 3
• A ferritin cut-off of 45 μg/L provides optimal sensitivity and specificity for diagnosing iron deficiency in clinical practice 2
• Measure transferrin saturation (TSAT), which is more sensitive than hemoglobin alone for detecting iron deficiency 1
• The combination of low MCV with RDW >14.0% (this patient has 15.6%) strongly suggests iron deficiency anemia rather than thalassemia minor, which typically presents with RDW ≤14.0% 1, 2

Treatment Protocol

First-Line Therapy

• Prescribe ferrous sulfate 200 mg orally three times daily, providing approximately 65 mg elemental iron per tablet 2
• Add ascorbic acid (vitamin C) to enhance iron absorption 1, 2
• Alternative formulations include ferrous gluconate or ferrous fumarate if the patient cannot tolerate ferrous sulfate due to gastrointestinal side effects 1
• Continue treatment for at least three months after anemia correction to fully replenish iron stores 1, 2

Expected Response

• A good response is defined as hemoglobin rise ≥10 g/L (≥1 g/dL) within 2 weeks, which confirms iron deficiency 1, 2
• If no response occurs within 4 weeks, expect hemoglobin increase of at least 2 g/dL with appropriate therapy 1

Monitoring Strategy

• Check hemoglobin and red cell indices at 2 weeks to confirm response to therapy 1
• Monitor at three-monthly intervals for one year, then again after a further year 1
• Provide additional oral iron if hemoglobin or MCV falls below normal during follow-up 1
• Monitor serum ferritin and TSAT to assess iron store repletion 2, 4

Investigation of Underlying Cause

Simultaneously investigate the source of iron loss, as iron deficiency in a 51-year-old female requires explanation:

• Evaluate for gastrointestinal blood loss through history of melena, hematochezia, or occult bleeding 5, 6
• Assess menstrual blood loss patterns, though approaching menopause, heavy menstrual bleeding remains possible 3
• Consider gastrointestinal malabsorption disorders if dietary history suggests inadequate intake 5
• Screen for celiac disease if malabsorption is suspected 5

Management of Treatment Failure

If the patient fails to respond to oral iron therapy after 4 weeks:

• Consider intravenous iron if malabsorption is present, with expected hemoglobin increase of at least 2 g/dL within 4 weeks 1
• Evaluate for genetic disorders of iron metabolism or heme synthesis, particularly if ferritin is low-normal (>20 mg/L) with low TSAT, or if there is family history of refractory anemia 5
• Test for thalassemia trait if RDW normalizes but MCV remains low 1, 2
• Consider hemoglobin electrophoresis to rule out hemoglobinopathies 6

Critical Pitfalls to Avoid

• Do not overlook combined deficiencies: Iron deficiency can coexist with vitamin B12 or folate deficiency 2, 4
• Do not assume all microcytic anemia is iron deficiency: Anemia of chronic disease, thalassemia, and sideroblastic anemia must be differentiated to avoid unnecessary iron therapy 5, 6
• Do not continue empiric iron therapy indefinitely without confirming diagnosis: Measure ferritin before starting treatment when possible 3, 6
• Do not ignore the need to identify the underlying cause: Iron deficiency is a diagnosis that requires explanation, particularly regarding blood loss 6

Special Considerations for Genetic Causes

If iron studies reveal elevated ferritin and/or TSAT, or low TSAT with low-normal ferritin (>20 mg/L), consider genetic disorders:

• Iron-refractory iron deficiency anemia (IRIDA) due to TMPRSS6 defects may require intravenous iron supplementation, as oral iron is typically ineffective 1, 2
• Monitor serum ferritin to not exceed 500 μg/L to avoid iron overload toxicity, especially in genetic forms 1, 4
• Sideroblastic anemia may respond to pyridoxine (vitamin B6) 50-200 mg daily if ALAS2 defects are identified 1, 4
• Family screening and genetic counseling are important if hereditary forms are suspected 2, 4