Haemoglobulinopathy Flashcards
(36 cards)
What is the problem in thalassaemia?
There is an imbalance of alpha and beta globin chain production, resulting in ineffective erythropoesis and haemolysis
What are the two broad subtypes of thalassaemia?
alpha thalassaemia and beta thalassaemia
What is usually the genetic cause of alpha thalassaemia?
Mostly gene deletions causing overproduction of beta chains
What is usually the genetic cause of beta thalassaemia?
Mostly point mutations causing overproduction of alpha chains
What is the difference between the main two types of beta thalassaemia?
Major: homozygous - this is present in the first year of life and requires lifelong transfusions
Minor: heterozygous - this is usually asymptomatic or causes a mild clinical picture
What are the features of beta thalassaemia major?
Presents between 3-6 months Hepatosplenomegaly Bony expansion/bony deformities Anaemia Iron accumulation (repeated blood transfusions)
What can iron overload due to recurrent transfusions do to a baby with beta thalassaemia major?
Failure of sexual development
Diabetes
Hepatic and cardiac dysfunction
What does the severity of alpha thalassaemia depend on?
The number of alpha chains missing
How do varying numbers of alpha chains affect patients?
4 chains missing - incompatible with life
3 missing - moderate anaemia and splenomegaly
1/2 missing - mild anaemia/asymptomatic
Where are beta genes located?
Chromosome 11
How many beta genes are there per chromosome?
1
Where are alpha genes located?
Chromosome 16
How many alpha genes are there per chromosome?
2
What does HbA consist of?
2 alpha chains and 2 beta chains
What does HbA2 consist of?
2 alpha chains and 2 delta chains
In what condition is there increases levels of HbA2?
Beta thalassaemia
What mutation is it that usually causes alpha thalassaemia?
Deletion of one or both of the genes on chromosome 16
How is alpha thalassaemia trait treated?
Usually asymptomatic - no treatment required
How does haemoglobin H disease present?
Wide spectrum: anaemia to transfusion dependant
Splenomegaly
Jaundice due to haemolysis
What is the pathogenesis of HbH disease?
Only one alpha gene working
How is HbH disease managed?
Folic acid supplementation
Transfusions if unwell - alpha is usually mild
Splenectomy if severe
What is the severest form of alpha thalassaemia??
Hb Bart’s Hydrops Fetalis Syndrome
What mutation is it that usually causes beta thalassaemia?
Point mutation
What mode of inheritance is beta thalassaemia?
Autosomal recessive
