What is the most likely diagnosis and recommended management for a patient with low hemoglobin, low hematocrit, low mean corpuscular volume, low mean corpuscular hemoglobin, low mean corpuscular hemoglobin concentration, elevated red‑cell distribution width, and normal white‑blood‑cell and platelet counts?

Microcytic Hypochromic Anemia: Iron Deficiency Anemia

This patient has iron deficiency anemia (IDA), characterized by the classic triad of low hemoglobin (11.8 g/dL), microcytosis (MCV 73.4 fL), and hypochromia (MCH 22.7 pg, MCHC 31.0 g/dL), with elevated RDW (16.3%) indicating anisocytosis from mixed populations of iron-deficient and normal red cells. 1, 2

Diagnostic Confirmation Required

Order a complete iron panel immediately (serum ferritin, transferrin saturation, and C-reactive protein) because low MCH and MCHC indicate hypochromic anemia most commonly caused by iron deficiency, and these tests are required to confirm the diagnosis and guide treatment. 2

Iron Study Interpretation

• Ferritin <15 μg/L confirms absent iron stores; <30 μg/L indicates low body iron stores in patients without inflammation 2
• Transferrin saturation <16-20% supports iron deficiency and is less affected by inflammation than ferritin 2
• If CRP is elevated (indicating inflammation), use higher ferritin thresholds of 45-100 μg/L to diagnose iron deficiency, as ferritin is an acute-phase reactant that can mask true iron deficiency 2
• Ferritin >150 μg/L makes absolute iron deficiency unlikely even with inflammation 2

Differential Diagnosis When Iron Studies Are Normal

If iron studies are normal despite the microcytic hypochromic picture:

• Obtain hemoglobin electrophoresis to evaluate for thalassemia trait, especially in patients of Mediterranean, African, or Southeast Asian descent 2
• Thalassemia minor produces microcytic anemia with low MCHC but can be distinguished by a normal or low RDW (<14.0%), whereas this patient has elevated RDW (16.3%), making thalassemia less likely 1
• Consider anemia of chronic disease or sideroblastic anemia as alternative diagnoses 2

Treatment Protocol for Confirmed Iron Deficiency

First-Line: Oral Iron Therapy

Initiate ferrous sulfate 325 mg (65 mg elemental iron) once daily between meals, as recent evidence shows intermittent dosing is as effective as daily or twice-daily dosing with fewer side effects 3

• Expect hemoglobin increase of approximately 1-2 g/dL every 2-4 weeks 2
• Continue iron supplementation for 3-6 months after hemoglobin normalizes to replenish iron stores 2
• Check hemoglobin, reticulocytes, and iron studies after 4-8 weeks of therapy 2
• A rise in hemoglobin ≥1 g/dL within 2 weeks strongly confirms iron deficiency, even if initial iron studies were equivocal 2

Second-Line: Intravenous Iron

Consider parenteral iron if the patient is intolerant to oral iron, has poor response to oral iron, or has severe anemia requiring rapid correction 2

For IV iron administration:

• Ferric carboxymaltose 750 mg intravenously in two doses separated by at least 7 days (total cumulative dose 1,500 mg) for patients ≥50 kg 4
• For patients <50 kg, administer 15 mg/kg body weight in two doses separated by at least 7 days 4
• Monitor serum phosphate levels in patients requiring repeat courses within 3 months, as hypophosphatemia is a known complication 4

Mandatory Investigation of Underlying Cause

Do not forget to investigate the source of iron deficiency, as it often indicates ongoing blood loss requiring evaluation, particularly gastrointestinal bleeding or malabsorption 2

Key investigations include:

• Gastrointestinal evaluation (upper endoscopy and colonoscopy) for occult bleeding 2
• Menstrual history in women of reproductive age 3
• Dietary assessment for inadequate iron intake 5
• Celiac serology if malabsorption suspected 2

Critical Pitfalls to Avoid

• Do not rely on MCV alone, as iron deficiency can present with normal MCV in early stages, and MCH (which is low in this patient) may be more sensitive 2
• Do not dismiss normal ferritin in inflammatory states—use the higher cutoff of 45-100 μg/L depending on inflammation severity 2
• Do not use excessive "milking" of the finger during capillary blood sampling, as this contaminates blood with tissue fluid leading to falsely low hemoglobin readings 5
• Confirm low readings with a second sample before initiating treatment 5