What is the likely diagnosis and recommended evaluation and management for a 10‑year‑old girl with mild microcytic anemia (hemoglobin 10.6 g/dL, hematocrit 33.7 %, mean corpuscular volume 74 fL, mean corpuscular hemoglobin 23.1 pg, mean corpuscular hemoglobin concentration 31.5 g/dL)?

Likely Diagnosis: Iron Deficiency Anemia

This 10-year-old girl has mild microcytic anemia (hemoglobin 10.6 g/dL, MCV 74 fL) that is most consistent with iron deficiency anemia, and she should be started immediately on oral iron supplementation at 3 mg/kg per day of elemental iron given between meals while simultaneously investigating the underlying cause. 1, 2

Diagnostic Confirmation

Laboratory Interpretation

• Her hemoglobin of 10.6 g/dL falls just below the anemia threshold of 11.0 g/dL for children aged 5-11 years, classifying this as mild anemia. 1, 2
• The MCV of 74 fL is significantly below the normal range (80-100 fL), confirming microcytic anemia. 3, 4
• The MCH of 23.1 pg and MCHC of 31.5 g/dL are both reduced, indicating hypochromic red cells characteristic of iron deficiency. 1

Essential Next Laboratory Tests

Order a complete iron panel including serum ferritin, transferrin saturation, serum iron, total iron-binding capacity, and red cell distribution width (RDW) to confirm iron deficiency. 1, 2

• Serum ferritin <30 μg/L confirms iron deficiency in the absence of inflammation. 1, 2
• If ferritin is 30-100 μg/L, add C-reactive protein (CRP) to assess for inflammation that may falsely elevate ferritin. 1, 2
• Transferrin saturation <16-20% strongly supports iron deficiency. 1
• RDW >14% combined with low MCV indicates iron deficiency anemia, while RDW ≤14% with low MCV suggests thalassemia trait. 1, 2, 5

Differential Diagnosis Considerations

While iron deficiency is most likely, thalassemia trait must be excluded, especially if the patient has Mediterranean, Middle Eastern, African, or Southeast Asian ancestry. 1, 4

• If iron studies are normal or near-normal with persistent microcytosis, order hemoglobin electrophoresis to evaluate for beta-thalassemia trait (elevated HbA2 >3.5%). 1, 4
• The Mentzer index (MCV/RBC count) can help distinguish: a value <13 suggests thalassemia trait, while >13 suggests iron deficiency. 5

Immediate Treatment Protocol

Iron Supplementation

Start oral elemental iron at 3 mg/kg per day, administered between meals (not with food or milk) to maximize absorption. 2

• Ferrous sulfate is the first-line formulation; alternatives include ferrous gluconate or ferrous fumarate if not tolerated. 1
• Adding vitamin C (ascorbic acid) with the iron dose enhances absorption. 1, 2

Dietary Modifications

Limit cow's milk intake to ≤24 oz (720 mL) per day, as excessive milk consumption is a major contributor to iron deficiency in children. 2

• Provide iron-fortified cereals daily. 2
• Include vitamin C-rich foods (fruits, vegetables) with meals to enhance non-heme iron absorption. 2
• Introduce iron-rich foods such as lean meats, which provide highly bioavailable heme iron. 2

Monitoring Response

Repeat hemoglobin or hematocrit at 4 weeks to confirm diagnosis and assess response. 2

• An increase of ≥1 g/dL in hemoglobin or ≥3% in hematocrit confirms iron deficiency anemia and indicates adequate response. 2
• If response criteria are met, continue iron supplementation for an additional 2-3 months to replenish iron stores. 1, 2
• If anemia persists after 4 weeks despite adherence, obtain complete iron studies and consider hemoglobin electrophoresis. 2

Investigation of Underlying Cause

Age-Specific Considerations

In a 10-year-old girl, the most common causes of iron deficiency are inadequate dietary intake, rapid growth, and in post-menarchal girls, menstrual blood loss. 6, 1

Dietary Assessment

Evaluate for restrictive diets (vegetarian, vegan, no red meat) that increase risk of iron deficiency. 6

• Plant-based (non-heme) iron is less well absorbed than meat-based (heme) iron. 6

Menstrual History (if applicable)

If the patient has reached menarche, assess for heavy menstrual bleeding, which is a leading cause of iron deficiency in adolescent females. 6, 1

Gastrointestinal Evaluation

While gastrointestinal blood loss is less common in children than adults, consider celiac disease screening if there are suggestive symptoms (chronic diarrhea, abdominal pain, poor growth) or if anemia fails to respond to iron therapy. 1, 7

Critical Pitfalls to Avoid

• Do not delay iron supplementation while awaiting ferritin results in a child with clear microcytic anemia and typical risk factors, given the high prevalence of iron deficiency in this age group. 2
• Do not administer iron with meals or milk, as this markedly reduces absorption and can cause treatment failure. 2
• Do not discontinue iron therapy prematurely after hemoglobin normalizes; continue for the full 2-3 months to restore iron stores. 1, 2
• Do not assume all microcytic anemia is iron deficiency—thalassemia trait, anemia of chronic disease, and lead toxicity must be considered if iron studies are inconsistent or response to therapy is inadequate. 1, 4
• Do not overlook combined deficiencies—iron deficiency can coexist with vitamin B12 or folate deficiency, recognizable by elevated RDW. 1

When to Refer to Pediatric Hematology

Refer if anemia does not respond to appropriate iron therapy after 4 weeks despite documented compliance. 2

• Refer if iron studies suggest thalassemia trait or other hemoglobinopathy. 1, 2
• Refer if the cause remains unclear after extended workup. 2
• Refer if there is extreme microcytosis (MCV <70 fL) or family history of refractory anemia, which may suggest rare genetic disorders of iron metabolism. 1