Hisam Siddiqi: Haemoglobinopathy Basics – A Quick Guide to Thalassaemia
Hisam Siddiqi, Consultant Haematologist at LycaHealth, The Blackheath Hospital, Dartford and Gravesham NHS Trust, shared a post on LinkedIn:
“Haemoglobinopathy Basics: A Quick Guide to Thalassaemia
When faced with a patient with microcytic anaemia, don’t forget to think beyond iron deficiency!
Clues from the Full Blood Count (FBC)
Typical thalassaemia pattern:
- Low Haemoglobin (Hb)
- Elevated RBC count (often surprisingly high)
- Low MCV (microcytosis)
- Low MCH (hypochromia)
A low MCV with a normal or elevated RBC count is a classic clue.
1.Alpha (α) Thalassaemia
Alpha globin production depends on 4 α-globin genes.
Gene deletions and clinical outcomes:
- αα/αα is Normal
- αα/α- is Silent carrier
- αα/– or α-/α- is α-thalassaemia trait – Mild microcytosis, Usually asymptomatic
- α-/– is HbH disease – Moderate anaemia, Splenomegaly may occur, Markedly reduced MCV
- –/– is Hb Bart’s hydrops fetalis – Severe disease, Usually incompatible with life
More common in:
- Southeast Asia
- Mediterranean populations
- African populations
2.Beta (β) Thalassaemia
β-thalassaemia results from reduced or absent β-globin chain production.
Normal adult haemoglobin: HbA is α₂β₂
When β chains are reduced, Excess α chains accumulate, More δ chains combine with α chains, and HbA₂ (α₂δ₂) increases
HbA₂ Interpretation (Normal is approximately 2-3.5%)
- Raised HbA₂
Think: β-thalassaemia trait,Vitamin B12 deficiency, Folate deficiency, Some antiretroviral therapies - Normal HbA₂
Think: α-thalassaemia - Reduced HbA₂
Think: α-thalassaemia, δ-thalassaemia, δβ-thalassaemia
β-Thalassaemia Genotypes
- β/β is Normal
- β⁰/β or β⁺/β is Thalassaemia trait
- β⁺/β⁺ or β⁰/β⁺ is Variable severity
- β⁰/β⁰ is Thalassaemia major – Severe anaemia in infancy, Early transfusion dependence
Take-Home Message
When you see:
- Very low MCV
- Low MCH
- Relatively high RBC count
- Iron studies not fitting iron deficiency
Think thalassaemia and check haemoglobin electrophoresis and HPLC before prescribing iron.”
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