Thalassemia

Question 1

Alpha Thalssemia

Answer 1

Alpha-thalassaemia is due to a deficiency of alpha chains in haemoglobin

Overview
2 separate alpha-globulin genes are located on each chromosome 16

Clinical severity depends on the number of alpha globulin alleles affected:
If 1 or 2 alpha globulin alleles are affected then the blood picture would be hypochromic and microcytic, but the Hb level would be typically normal
If are 3 alpha globulin alleles are affected results in a hypochromic microcytic anaemia with splenomegaly. This is known as Hb H disease
If all 4 alpha globulin alleles are affected (i.e. homozygote) then death in utero (hydrops fetalis, Bart’s hydrops)

Question 2

Beta Thalassemia

Answer 2

The thalassaemias are a group of genetic disorders characterised by a reduced production rate of either alpha or beta chains. Beta-thalassaemia trait is an autosomal recessive condition characterised by a mild hypochromic, microcytic anaemia. It is usually asymptomatic

Features
mild hypochromic, microcytic anaemia - microcytosis is characteristically disproportionate to the anaemia
HbA2 raised (> 3.5%)

Question 3

Beta Thalassemia Major

Answer 3

Overview
absence of beta globulin chains
chromosome 11

Features
presents in the first year of life with failure to thrive and hepatosplenomegaly
microcytic anaemia
HbA2 & HbF raised
HbA absent

Management
repeated transfusion
this leads to iron overload → organ failure
iron chelation therapy is therefore important (e.g. desferrioxamine)