What is the appropriate diagnosis and management for a 39-year-old female with microcytic, hypochromic anemia and thrombocytosis?

Microcytic Hypochromic Anemia with Thrombocytosis

This patient has iron deficiency anemia until proven otherwise, and should immediately have serum ferritin, transferrin saturation, and RDW checked to confirm the diagnosis before starting oral ferrous sulfate 200 mg three times daily. 1

Diagnostic Interpretation

The laboratory values reveal severe microcytic, hypochromic anemia with reactive thrombocytosis:

• MCV 73.7 fL (microcytic), MCH 21.1 pg (hypochromic), and MCHC 28.7 g/dL (hypochromic) strongly suggest iron deficiency anemia in a 39-year-old premenopausal woman 1
• Platelet count 496 represents reactive thrombocytosis, which commonly accompanies iron deficiency anemia and resolves with iron repletion 1
• The combination of microcytosis with thrombocytosis is highly characteristic of iron deficiency rather than thalassemia trait 2

Immediate Diagnostic Workup

Order these tests immediately to confirm iron deficiency:

• Serum ferritin is the single most useful marker: <15 μg/L confirms absent iron stores with 99% specificity, <30 μg/L indicates low stores, and <45 μg/L is the optimal cutoff for sensitivity/specificity 1, 2
• Transferrin saturation (TSAT) is more sensitive than hemoglobin alone for detecting iron deficiency; <16% suggests iron deficiency 1
• Red cell distribution width (RDW): if >14.0% with low MCV, this strongly confirms iron deficiency anemia rather than thalassemia trait 1, 2
• Peripheral blood smear to evaluate red cell morphology 2

Differential Diagnosis Considerations

While iron deficiency is most likely, the MCV of 73.7 requires consideration of:

• Thalassemia trait: However, this typically presents with RDW ≤14.0%, MCV disproportionately low relative to anemia severity, and normal/elevated ferritin 1, 2
• Anemia of chronic disease: Shows low iron with decreased total iron-binding capacity and ferritin >100 μg/L 1, 3
• Genetic disorders of iron metabolism: Unlikely at age 39 without prior diagnosis, but consider if ferritin is normal/elevated (>20 μg/L) with low TSAT 1

Treatment Protocol

Once iron deficiency is confirmed (ferritin <45 μg/L with elevated RDW):

• Start ferrous sulfate 200 mg (65 mg elemental iron) three times daily for at least 3 months after anemia correction to replenish iron stores 1, 2
• Add ascorbic acid (vitamin C) to enhance iron absorption 1
• Alternative formulations (ferrous gluconate or ferrous fumarate) if gastrointestinal side effects occur 1
• Expected response: hemoglobin rise ≥10 g/L (≥1 g/dL) within 2 weeks confirms iron deficiency 1, 4

Investigation of Underlying Cause

In a 39-year-old premenopausal woman, investigate these sources of iron loss:

• Heavy menstrual bleeding is the most common cause in this demographic 1
• Gastrointestinal blood loss must be excluded, especially if menstrual history is unremarkable 1, 2
• Dietary inadequacy or malabsorption (consider celiac disease screening if malabsorption suspected) 1
• Fast-track GI referral is warranted for non-menstruating women with Hb <100 g/L (10 g/dL) with confirmed iron deficiency 1

Monitoring Strategy

• Check hemoglobin at 2 weeks: expect ≥1 g/dL rise if iron deficiency is the cause 1, 4
• Monitor hemoglobin and red cell indices at 3-month intervals for one year, then annually 1, 4
• Expect hemoglobin increase of at least 2 g/dL within 4 weeks of starting oral iron 1, 4
• Continue iron for at least 3 months after anemia correction to replenish stores 1, 2
• Platelet count should normalize as iron deficiency resolves 1

Critical Pitfalls to Avoid

• Do not start iron empirically without confirming iron deficiency: if ferritin is normal/elevated (>20 μg/L) despite microcytosis, order hemoglobin electrophoresis to evaluate for thalassemia trait, particularly with Mediterranean, African, Middle Eastern, or Southeast Asian ancestry 1, 2
• Do not assume all microcytic anemia is iron deficiency: anemia of chronic disease, thalassemia, and sideroblastic anemia must be differentiated 1, 3
• Do not overlook combined deficiencies: iron deficiency can coexist with B12 or folate deficiency 1
• If patient fails to respond to oral iron within 2-4 weeks, consider non-compliance, ongoing blood loss, malabsorption, or rare genetic disorders requiring intravenous iron 1

Special Consideration for Intravenous Iron

Consider IV iron if:

• Malabsorption is present (celiac disease, inflammatory bowel disease) 1
• Patient cannot tolerate oral iron despite trying alternative formulations 1
• Ongoing losses exceed oral replacement capacity 1
• Genetic disorders like IRIDA are diagnosed (though unlikely at age 39 without prior diagnosis) 1