Abnormalities with blood cells Flashcards
(27 cards)
What makes up haemoglobin?
2 alpha chains
2 beta chains
Both associated with a haem group
Which type of hemoglobin is most common?
Hb A
What is different about Hb A2?
Less common variety
2 delta chains instead of 2 beta chains
How can haemoglobinopathies be classified?
Structural variants
Thalassaemia
What causes a structural variant?
Mutation changes an amino acid in the globin chain
What causes a thalassaemia?
Mutation that results in a reduced production of the globin chain
What are the types of thalassaemia?
Alpha
Beta
What causes alpha thalassaemia?
Mostly caused by a mutation to one of the 4 alpha globin genes?
What are the 3 severities of alpha thalassaemia?
Alpha thalassaemia trait
Hb H disease
Hb Bart’s hydrops fetalis
What causes alpha thalassaemia trait?
The loss of 1/2 alpha globin genes
What causes Hb H disease?
The loss of 3 alpha globin genes
What causes Hb Bart’s hydrops fetalis?
The loss of all 4 alpha globin genes
What are the symptoms of Hb H disease?
Moderately severe microcytic anaemia
Splenomegaly
What does Hb Bart’s hydrops fetalis result in?
No production of Hb F, Hb A or Hb A2 without alpha globin
Incompatible with life
What causes beta thalassaemia?
Mostly point mutations which results in the reduced production of the beta globin chain
Either no amount of chain synthesised (βo) or small amounts synthesised (β+)
Leads to an excess of alpha chains which causes ineffective erythropoiesis and haemolysis
What does the excess of alpha chains in beta thalassaemia cause?
Ineffective erythropoiesis and haemolysis
What are the severities of beta thalassaemia? (including potential phenotypes)
Beta thalassaemia trait (o ββ+ or ββo)
Beta thalassaemia intermedia (o βoβ+ or β+β+)
Beta thalassaemia major (o βoβo)
What are the symptoms of beta thalassaemia major?
Severe anaemia preseting in early life - will lead to death within first decade if untreated
Bony deformation
Splenomegaly and hepatomegaly
Wasting of limbs and stunted growth
What are the symptoms of beta thalassaemia intermedia?
Mild-moderate anaemia
What are the symptoms of beta thalassaemia trait?
Mild anaemia
What causes sickle cell disease?
Inherit what and what is different about it
Inheritance of homozygous recessive sickle beta globin gene (Hb BS)
Substitution of valine for glutamic acid in position 6 in the beta chain
Why is sickle cell so well maintained?
Being a carrier doesn’t normally produce symptoms
Seems to give a degree of protection against malaria
In what conditions may sickle cell carriers exhibit symptoms?
At very low oxygen tensions
Under anaesthetics
At altitude
What are the clinical features of sickle cell disease?
Haemolytic anaemia punctured with crises
