Question

A 16 year old girl presents with a history of fatiguability, weakness and lethargy. The complete blood count (CBC) reveals a haemoglobin of 7.0 g/dL, MCV of 70 fL, MCH of 20 pg/cell and a red cell distribution width (RDW) of 20. The most likely diagnosis is:

• A. Iron deficiency anaemia
• B. Thalassaemia minor
• C. Thalassaemia major
• D. Sickle cell trait

Hint:

High RDW with microcytosis favours iron deficiency over thalassaemia trait.

Answer 1

The Correct Option is A

Step 1: Read the indices. Hb 7.0 g/dL is anaemia. MCV 70 fL (<80) and MCH 20 pg (<27) make it a microcytic hypochromic anaemia. The key extra clue is RDW of 20, which is high (normal about 11.5 to 14.5).
Step 2: Recall what high RDW means. RDW measures variation in red cell size (anisocytosis). It is HIGH in iron deficiency anaemia because the marrow makes cells of mixed size as iron runs low.
Step 3: Contrast with thalassaemia. In thalassaemia minor the cells are uniformly small, so RDW is usually NORMAL even though MCV is low. A high RDW therefore points away from thalassaemia minor and toward iron deficiency.
Step 4: Reject the rest. Thalassaemia major presents in early childhood with very severe anaemia and transfusion dependence, not a fresh teenage presentation. Sickle cell trait is usually asymptomatic with a normal or near-normal blood picture, not microcytic anaemia with Hb 7.
Step 5: Microcytic hypochromic anaemia with HIGH RDW in a teenage girl (menstrual loss is common) fits iron deficiency best.
Answer: A. Iron deficiency anaemia.