Thalassaemia Flashcards
Aetiology of thalassaemia?
Thalassaemia is related to a genetic defect in the protein chains that make up haemoglobin. Normal haemoglobin consists of 2 alpha and 2 beta-globin chains.
Defects in alpha-globin chains leads to alpha thalassaemia. Defects in the beta-globin chains leads to beta thalassaemia. Both conditions are autosomal recessive. The overall effect is varying degrees of anaemia depends on the type and mutation.
Pathophysiology of thalassaemia?
In thalassaemia, the red blood cells are more fragile and break down more easily. The spleen acts as a sieve to filter the blood and remove older blood cells. In thalassaemia the spleen collects all the destroyed red blood cells and swells, resulting in splenomegaly.
The bone marrow expands to produce extra red blood cells to compensate for the chronic anaemia. This causes a susceptibility to fractures and prominent features such as a pronounced forehead and malar eminences (cheekbones).
Potential signs and symptoms of thalassaemia?
Microcytic anaemia (low mean corpuscular volume)
Fatigue
Pallor
Jaundice
Gallstones
Splenomegaly
Poor growth and development
Pronounced forehead and malar eminences
Diagnosis of thalassaemia?
Full blood count shows a microcytic anaemia.
Haemoglobin electrophoresis is used to diagnose globin abnormalities.
DNA testing can be used to look for the genetic abnormality
Iron overload + thalassaemia
Iron overload occurs in thalassaemia as a result of faulty creation of red blood cells, recurrent transfusions and increased absorption of iron in response to the anaemia.
Patients with thalassaemia have serum ferritin levels monitored to check for iron overload. Management involves limiting transfusions and iron chelation.
Iron overload in thalassaemia causes effects similar to haemochromatosis:
Fatigue
Liver cirrhosis
Infertility and impotence
Heart failure
Arthritis
Diabetes
Osteoporosis and joint pain
Alpha-thalassaemia: management
Alpha-thalassaemia is caused by defects in alpha-globin chains. The gene coding for this protein is on chromosome 16.
Management:
Monitoring the full blood count
Monitoring for complications
Blood transfusions
Splenectomy may be performed
Bone marrow transplant can be curative
Beta-thalassemia can be split into 3 types:
Beta-thalassaemia is caused by defects in beta-globin chains. The gene coding for this protein is on chromosome 11.
The genes defect can either consist of abnormal copies that retain some function or deletion genes where there is no function in the beta-globin protein at all. Based on this, beta-thalassaemia can be split into three types:
Thalassaemia minor
Thalassaemia intermedia
Thalassaemia major
Thalassaemia minor?
Patients with beta thalassaemia minor are carriers of an abnormally functioning beta globin gene. They have one abnormal and one normal gene.
Thalassaemia minor causes a mild microcytic anaemia and usually patients only require monitoring and no active treatment.
Thalassaemia intermedia
Patients with beta thalassaemia intermedia have two abnormal copies of the beta-globin gene. This can be either two defective genes or one defective gene and one deletion gene.
Thalassaemia intermedica causes a more significant microcytic anaemia and patients require monitoring and occasional blood transfusions. If they need more transfusions they may require iron chelation to prevent iron overload.
Thalassaemia major
Patients with beta thalassaemia major are homozygous for the deletion genes. They have no functioning beta-globin genes at all. This is the most severe form and usually presents with severe anaemia and failure to thrive in early childhood.
Thalassaemia major causes:
Severe microcytic anaemia
Splenomegaly
Bone deformities
Management involves regular transfusions, iron chelation and splenectomy. Bone marrow transplant can potentially be curative.
