MCQ: anemia | iron therapy | poor response | Mentzer index
A 13-year-old girl is evaluated for persistent microcytic anemia. She has completed 3 months of therapeutic-dose oral iron therapy with good compliance, but her hemoglobin has not improved. She is otherwise healthy and has no history of chronic illness or excessive menstrual bleeding.
Investigations:
- Hemoglobin: 10.4 g/dL
- RBC count: 6.4 × 10¹²/L
- MCV: 61 fL
- RDW: 12.8%
- Serum ferritin: 72 ng/mL
The Mentzer index (MCV/RBC count) is 9.5.
What is the most likely diagnosis?
A. Anemia of chronic disease
B. β-thalassemia trait (minor)
C. Iron deficiency anemia
D. Lead poisoning
E. Sideroblastic anemia
Correct answer & Explanation:
Correct answer : B. β-thalassemia trait.(minor)
Explanation: Thalassemia minor
This child has the classic features of β-thalassemia trait (minor):
- Mild microcytic anemia
- No response to adequate iron therapy
- Normal serum ferritin, excluding iron deficiency
- High RBC count despite low MCV
- Normal RDW
- Mentzer index <13, which strongly favors thalassemia trait over iron deficiency anemia
Although hemoglobin electrophoresis (elevated HbA₂) would confirm the diagnosis, the clinical and hematological findings are already highly suggestive of β-thalassemia trait.
Why the other options are incorrect
A. Anemia of chronic disease
- Usually normocytic or mildly microcytic with evidence of chronic inflammation and a low/normal RBC count.
C. Iron deficiency anemia
- Typically has low ferritin, high RDW, Mentzer index >13, and responds to iron therapy.
D. Sideroblastic anemia
- Less common in children and diagnosed by bone marrow examination showing ring sideroblasts.
E. α-thalassemia major
- Causes Hb Bart’s hydrops fetalis and is incompatible with survival without intensive fetal/neonatal intervention.
High-yield pearl
A child with persistent microcytic anemia despite adequate iron therapy, normal ferritin, high RBC count, and a Mentzer index <13 should be presumed to have thalassemia trait until proven otherwise. Avoid unnecessary prolonged iron supplementation unless iron deficiency is also documented.
