What is the diagnosis and management for a 39-year-old patient with microcytic anemia, hypochromia, and thrombocytosis?

Diagnosis: Iron Deficiency Anemia with Reactive Thrombocytosis

This patient has iron deficiency anemia (IDA) based on the severe microcytosis (MCV 73.7), hypochromia (MCH 21.2, MCHC 28.7), and reactive thrombocytosis (platelet 496), and should be treated with oral ferrous sulfate 200 mg three times daily while investigating the underlying cause of iron loss. 1, 2, 3

Laboratory Interpretation

The laboratory values definitively indicate iron deficiency:

• MCV 73.7 fL represents severe microcytosis (normal >80), which is the hallmark of iron deficiency 1, 3
• MCH 21.2 pg and MCHC 28.7 g/dL confirm hypochromia, indicating inadequate hemoglobin synthesis from iron deficiency 2, 3
• Platelet count 496 represents reactive thrombocytosis, commonly seen with iron deficiency as a compensatory response 1, 2
• Hemoglobin 10.2 g/dL confirms moderate anemia requiring treatment 2, 3

Required Confirmatory Testing

Before initiating treatment, obtain these specific tests:

• Serum ferritin is the single most powerful diagnostic test: <15 μg/L confirms absent iron stores, <30 μg/L indicates low stores, and <45 μg/L provides optimal sensitivity/specificity 1, 2, 3
• Transferrin saturation (TSAT) <30% supports iron deficiency, particularly if ferritin is falsely elevated by inflammation 1, 2
• RDW (Red Cell Distribution Width) should be >14.0% in iron deficiency (distinguishes from thalassemia where RDW ≤14.0%) 2, 3

Critical caveat: Ferritin is an acute phase reactant and can be falsely elevated in inflammation, infection, malignancy, or liver disease—levels up to 100 μg/L may still indicate iron deficiency in these contexts 1, 2

Immediate Treatment Protocol

Start treatment now while investigating the cause:

• Ferrous sulfate 200 mg (65 mg elemental iron) three times daily for at least 3 months after hemoglobin normalizes to replenish iron stores 2, 3
• Add ascorbic acid to enhance iron absorption 2, 3
• Alternative formulations (ferrous gluconate or ferrous fumarate) if ferrous sulfate not tolerated 2, 3
• Expected response: Hemoglobin should rise ≥10 g/L (≥1 g/dL) within 2 weeks, confirming iron deficiency 1, 2, 3

Mandatory Investigation for Source of Iron Loss

At age 39, iron deficiency anemia requires explanation—do not simply treat without investigating:

• Menstrual history: Heavy menstrual bleeding is the most common cause in premenopausal women 2
• Gastrointestinal blood loss: Check for melena, hematochezia, or occult bleeding—consider GI referral if symptoms present 2, 3
• Dietary assessment: Evaluate for inadequate iron intake, though rarely the sole cause in adults 2, 3
• Malabsorption disorders: Screen for celiac disease if malabsorption suspected 2

Fast-track GI referral is warranted for non-menstruating women with Hb <100 g/L (10 g/dL), though investigation should be considered at any level of confirmed iron deficiency 2

Monitoring Protocol

• Recheck hemoglobin and MCV at 2 weeks to confirm response (expected rise ≥10 g/L) 1, 2, 3
• Monitor at 3-month intervals for one year, then recheck at 2 years 2, 3
• Continue iron for 3 months after hemoglobin normalizes to replenish stores 2, 3
• Provide additional iron if hemoglobin or MCV falls below normal during follow-up 2, 3

Alternative Diagnoses to Exclude

If ferritin is normal or elevated (>100 μg/L), consider:

• Thalassemia trait: Suggested by MCV disproportionately low relative to anemia, normal RDW (≤14.0%), elevated red cell count, and normal iron studies—requires hemoglobin electrophoresis 1, 2, 3
• Anemia of chronic disease: TSAT <20% with ferritin >100 μg/L 2
• Genetic disorders of iron metabolism (IRIDA, sideroblastic anemia): Consider if extreme microcytosis (MCV <70), family history, or failure to respond to oral iron 4, 1, 2

When to Consider Intravenous Iron

Switch to IV iron (iron sucrose or iron gluconate) if:

• Malabsorption present (celiac disease, inflammatory bowel disease) 2, 3
• Failure to respond to oral iron after 4 weeks (expected Hb increase ≥2 g/dL) 2, 3
• True intolerance to all oral formulations 2, 3

For genetic disorders like IRIDA (iron-refractory iron deficiency anemia), IV iron is required as oral iron is typically ineffective 4, 2

Critical Pitfalls to Avoid

• Do not assume dietary insufficiency or ethnic background explains microcytosis—laboratory confirmation is mandatory 1
• Do not overlook combined deficiencies—iron deficiency can coexist with B12 or folate deficiency 2
• Do not assume all microcytic anemia is iron deficiency—thalassemia, anemia of chronic disease, and sideroblastic anemia must be differentiated to avoid unnecessary iron therapy 2
• Do not stop investigating if patient responds to iron—the underlying cause of iron loss must still be identified and addressed 2, 3