Haemoglobinopathy Flashcards
Describe the structure of haemoglobin
Tetramer
4 globin chains
One haem group attached to each globin chain
What are the 3 main forms of haemoglobin?
HbA: (2-alpha, 2-beta)
HbA2: (2-alpha, 2-delta)
HbF: (2-alpha, 2-gamma)
The genes making the alpha protein for haemoglobin are located on which chromosome? How many alpha genes are on each chromosome?
Chromosome 16
2 alpha genes per chromosome
The genes making the beta protein for haemoglobin are located on which chromosome? How many beta genes are on each chromosome?
Chromosome 11
1 beta gene per chromosome
Which type of haemoglobin - HbA, HbA2 or HbF - is found in a foetus?
HbF
When does foetal haemoglobin typically reach adult level following birth?
6-12 months
What are haemoglobinopathies?
Hereditary conditions affecting globin chain synthesis
What inheritance pattern do haemoglobinopathies generally follow?
Autosomal recessive
What are the 2 main groups of haemoglobinopathies?
Thalassaemias
Structural variant
What is the problem in thalassaemias?
Decreased rate of globin chain synthesis, resulting in less haemoglobin
What is the problem in structural variant haemoglobinopathy?
Normal production of structurally abnormal globin chains, resulting in variant haemoglobin
Alpha thalassaemia (affecting alpha-chain synthesis) results from deletion of how many - one or both - alpha genes from chromosome 16?
Either! Can arise due to deletion of one alpha gene or both alpha genes
What are the 3 classifications of alpha thalassaemia?
Trait: 1 or 2 genes missing
HbH: 1 alpha gene left
Bart’s hydrops fetalis: no alpha genes
Alpha thalassaemia trait is usually asymptomatic. True/False?
True
Mild anaemia and may be mistaken for iron deficiency
Describe the clinical features of HbH alpha thalassaemia
Anaemia Very low MCV Splenomegaly Jaundice Growth retardation