Flashcards in Haemoglobinopathies Deck (118)
Describe the structure of haemoglobin (adult).
A tetramer made up of 2 alpha globin like chains and 2 beta globin like chains
One haem group attached to each globin chain
Globin chains keep haem _______, and protect it from _________
What are the 3 major forms of haemoglobin and what chains are these composed of?
* HbA = 2 alpha chains and 2 beta chains; α2β2.
* HbA2 = 2 alpha and 2 delta; α2δ2.
* HbF = 2 alpha and 2 gamma; α2γ2.
In adults, what proportion of the haemoglobin is made up of each of the above types?
HbA - 97%.
HbA2 - 2.5%.
Hbf - 0.5%.
What chromosome are alpha like genes on?
How many alpha genes are there per i) chromosome? ii) cell?
What chromosome are beta like genes on?
How many beta genes are there per i) chromosome? ii) cell?
When does the expression of globin genes change?
During embryonic life and childhood.
At what age are alpha Hb levels reached?
What are genes arranged in order of?
What are haemoglobinopathies?
Hereditary conditions affecting globin chain synthesis
What is the mode of hesitance of haemoglobinopathies?
What are the 2 main groups of haemoglobinopathies?
* Structural haemoglobin variants
What are thalassaemias?
Conditions where there is a decreased rate of globin chain synthesis
'Conditions where there is a decreased rate of globin chain synthesis' - name the condition.
What are structural haemoglobin variants?
Conditions where there is normal production of structurally abnormal globin chains - variant haemoglobin e.g. HbS.
What is a thalassaemia?
Reduced globin chain synthesis, resulting in impaired haemoglobin production
What are the 2 main groups of thalassaemias?
* Alpha thalassaemia; α chains affected.
* Beta thalassaemia; β chains affected.
What does the inadequate Hb production in thalassaemias result in?
Microcytic Hypochromic Anaemia.
Thalassaemias can be toxic. Explain why.
There is unbalanced accumulation of globin chains and this results in:
* Ineffective erythropoiesis
Why are thalassaemias imprortant?
They are the commonest myogenic disorder
What do the mutations in alpha thalassaemias affect?
α globin chain synthesis
How many alpha genes do unaffected individuals have?
4 - αα/αα.
What happens to alpha chains in alpha thalassaemia?
There is reduced α+ or absent α0 synthesis of α chains
What does an absent a chain result from?
Deletion of one α+ (-α) or both α0 (--) alpha genes from chromosome 16.
What type of Hb is affected in alpha thalassaemias?
HbA, HbA2 and HbF are all affected
Because alpha genes are present in all adult forms of Hb
What would the genes of someone without an alpha thalassaemia look like?
4 normal α genes (αα/αα).
What is an alpha thalassaemia trait?
Where there are one or two genes missing