Thalassaemia (zero to finals) Flashcards
What is thalassaemia?
An inherited blood disorder caused by a genetic defect in the protein chains that make up haemoglobin.
Normal haemoglobin consists of what chain types?
2 alpha chains and 2 beta chains
Defects in alpha-globin chains lead to alpha thalassaemia. True/false?
True
Defects in alpha-globin chains lead to alpha thalassaemia.
Defects in the beta-globin chains lead to beta thalassaemia.
Both conditions are autosomal recessive.
The overall effect is varying degrees of anaemia, depending on the type and mutation.
How can thalassaemia develop into haemolytic anaemia and how does this affect the spleen?
In patients with thalassaemia, the red blood cells are more fragile and break down easily, causing haemolytic anaemia.
The spleen acts as a sieve, filtering the blood and removing older cells. The spleen collects all the destroyed red blood cells, resulting in splenomegaly.
What are the features of thalassaemia?
Features are dependant on the type however the universal features are:
Microcytic anaemia (low mean corpuscular volume)
Fatigue
Pallor
Jaundice
Gallstones
Splenomegaly
Poor growth and development
Investigations for thalassaemia?
Microcytic anaemia (low mean cell volume) is a typical finding on a full blood count.
Raised ferritin suggests iron overload.
Haemoglobin electrophoresis is used to diagnose globin abnormalities.
DNA testing can be used to look for the genetic abnormality.
All pregnant women in the UK are offered a screening test for thalassaemia at booking.
When may iron overload occur in thalassaemia?
Increased iron absorption in the gastrointestinal tract
Blood transfusions
Iron overload in thalassaemia can result in what symptoms and complications?
Liver cirrhosis
Hypogonadism
Hypothyroidism
Heart failure
Diabetes
Osteoporosis
What causes alpha thalassaemia?
Defects in the alpha-globin chain
What chromosome hold the genes that code for alpha globin?
Chromosome 16
Management of alpha thalassaemia?
Monitoring
Blood transfusions
Splenectomy may be performed
Bone marrow transplant can be curative
What is HbH disease?
More severe form of alpha thalassaemia
Only one working α gene per cell (–/-α )
Anaemia with very low MCV (microcytic) and MCH
MCH = a measurement of the average amount of hemoglobin in each red blood cell.
Can there be a variation in symptoms for alpha thalassaemia?
Yes
The severity of symptoms varies depending on the type and number of genetic defects, ranging from entirely asymptomatic as a carrier, to moderate anaemia (haemoglobin H disease), to intrauterine death due to severe foetal anaemia (alpha thalassemia major).
What causes beta thalassaemia?
Defects in the beta-globin chain
What chromosome hold the genes that code for beta globin?
Chromosome 11
Do the beta-globin gene defects only consist of deletions?
No, the gene defects can either consist of abnormal copies that retain some function or deletion genes with no function in the beta-globin.
How many types of beta thalassaemia are there?
3 types
What are the 3 types of beta thalassaemia?
Thalassaemia minor
Thalassaemia intermedia
Thalassaemia major
What is thalassaemia minor?
Patients with beta thalassaemia minor (also called thalassaemia trait) are carriers of an abnormally functioning beta-globin gene.
They have one abnormal and one normal gene.
Can thalassemia minor cause microcytic anaemia and does it require treatment?
Thalassaemia minor causes mild microcytic anaemia and usually only requires monitoring.
What is thalassaemia intermedia?
Patients with beta thalassaemia intermedia have two abnormal copies of the beta-globin gene.
This can be either:
Two defective genes
One defective gene and one deletion gene
What can thalassaemia intermedia cause and what is the management for thalassaemia intermedia?
Thalassaemia intermedia causes more significant microcytic anaemia.
Patients require monitoring and may need occasional blood transfusions. They may require iron chelation to prevent iron overload.
What is thalassaemia major?
Patients with beta thalassaemia major are homozygous for the deletion genes.
They have no functioning beta-globin genes. This is the most severe form and usually presents with severe anaemia and failure to thrive in early childhood.
What effect does thalassaemia major have on the bone marrow and how does it increase fracture risk?
The bone marrow is under so much strain to produce extra red blood cells to compensate for the chronic anaemia that it expands enough to increase the risk of fractures and change the patient’s appearance.
What are some of the abnormal features relating to bone changes due to thalassaemia major?
Abnormal features relating to bone changes include:
Frontal bossing (prominent forehead)
Enlarged maxilla (prominent cheekbones)
Depressed nasal bridge (flat nose)
Protruding upper teeth
Management for thalassaemia major?
Management involves regular transfusions, iron chelation (removal of excess iron from body) and splenectomy.
A bone marrow transplant can be curative.
