What is the diagnosis and treatment for a patient with microcytic, hypochromic anemia, elevated Red Cell Distribution Width (RDW), low Mean Corpuscular Volume (MCV), and low Mean Corpuscular Hemoglobin (MCH)?

Microcytic Hypochromic Anemia with Elevated RDW

Most Likely Diagnosis: Iron Deficiency Anemia

The combination of low MCV, low MCH, and elevated RDW (>14%) strongly indicates iron deficiency anemia, which requires confirmation with serum ferritin and immediate investigation for the source of blood loss. 1, 2

Diagnostic Confirmation

The elevated RDW is the key distinguishing feature in your presentation:

• Low MCV + RDW >14.0% has 91.4% accuracy for iron deficiency anemia, while low MCV + RDW ≤14.0% suggests thalassemia minor 3, 2
• RDW is an indicator of iron deficiency and can detect early deficiency even before microcytosis develops 1
• The elevated RDW reflects the heterogeneous red cell population (anisocytosis) characteristic of iron deficiency, as older normocytic cells circulate alongside newly formed microcytic cells 4, 5

Essential Laboratory Workup

Serum ferritin is the single most powerful test to confirm iron deficiency:

• Ferritin <30 μg/L confirms iron deficiency in the absence of inflammation 2, 6
• Ferritin <45 μg/L provides optimal sensitivity and specificity in clinical practice 3, 6
• In the presence of inflammation (elevated CRP), ferritin up to 100 μg/L may still indicate iron deficiency 1, 2

Additional confirmatory tests:

• Transferrin saturation <16-20% supports iron deficiency and is more sensitive than hemoglobin alone 3, 6
• Reticulocyte count to assess bone marrow response (typically low or inappropriately normal in iron deficiency) 1
• Complete blood count with differential, CRP to assess for inflammation 1

Mandatory Investigation for Underlying Cause

All adults with confirmed iron deficiency require gastrointestinal evaluation to identify the source of blood loss - this is non-negotiable 2, 6:

• Men with Hb <110 g/L or non-menstruating women with Hb <100 g/L warrant fast-track GI referral 3
• Upper and lower endoscopy should be performed unless there is clear evidence of significant non-gastrointestinal blood loss 2
• In premenopausal women, assess for heavy menstrual bleeding as the most common cause 3
• Consider celiac disease screening if malabsorption is suspected 3

First-Line Treatment Protocol

Oral ferrous sulfate 200 mg (65 mg elemental iron) three times daily for at least 3 months after hemoglobin normalizes to replenish iron stores 3, 6, 7:

• Take tablets whole - do not crush or chew 7
• Add ascorbic acid (vitamin C) to enhance iron absorption 3, 6
• Alternative formulations include ferrous gluconate or ferrous fumarate if ferrous sulfate is not tolerated 3, 6

Expected Response and Monitoring

• Hemoglobin should rise ≥10 g/L (≥1 g/dL) within 2 weeks - this confirms iron deficiency 3, 2, 6
• Continue treatment for at least 3 months after anemia correction to replenish iron stores 6
• Monitor hemoglobin and MCV at 3-month intervals for one year, then at one additional year 3, 6
• Provide additional oral iron if hemoglobin or MCV falls below normal 3, 6

Management of Treatment Failure

If no response within 2-4 weeks, consider:

• Non-compliance or ongoing blood loss (most common causes) 3
• Malabsorption - switch to intravenous iron (iron sucrose or iron gluconate) with expected hemoglobin increase of at least 2 g/dL within 4 weeks 3, 6, 8
• Thalassemia trait - order hemoglobin electrophoresis if microcytosis with normal iron studies or MCV disproportionately low relative to degree of anemia 3, 6
• Anemia of chronic disease - typically shows ferritin >100 μg/L with transferrin saturation <20% 1, 2
• Combined deficiency (iron plus folate/B12) - may present with normal MCV but elevated RDW, requiring vitamin level checks 2
• Rare genetic disorders (IRIDA, sideroblastic anemia) - consider if extreme microcytosis (MCV <70) or family history present 3

Critical Pitfalls to Avoid

• Do not assume all microcytic anemia is iron deficiency - thalassemia and anemia of chronic disease must be differentiated to avoid unnecessary iron therapy 3
• Do not overlook combined deficiencies - iron deficiency can coexist with B12 or folate deficiency, which may mask each other's typical MCV changes 1, 3
• Do not fail to investigate the source of iron loss - iron deficiency in adults always requires explanation, particularly gastrointestinal blood loss or malignancy 3, 2
• In the presence of inflammation, ferritin can be falsely elevated - add transferrin saturation to the workup 1, 2