Haemoglobinopathy Flashcards
Describe the structure of haemoglobin?
2 alpha globin like chains
2 beta globin like chains
What is the ratio of haem to globin in haemaglobin?
One haem attached to each globin chain
What chromosome is the alpha like gene expressed on?
16
What chromosome is the beta like gene expressed on?
11
At what age do you reach adult levels of haemaglobin?
6 - 12 months
What are the two main groups of haemaglobinopathies?
Thalassaemia - decreased rate of globin chain production
Structural haemoglobin variants - normal production of structurally abnormal globin chains
What are the two types of thalassaemias?
Alpha thalassaemia
Beta thalassaemia
What kind of anaemia do you get with thalassaemia?
Microcytic hypochromic anaemia
Why do you get alpha thalassaemia?
Deletion of one or both of the alpha genes from chromosome 16
Why do you get reduced synthesis alpha thalassaemia?
Deletion of one of the alpha genes from chromosome 16
Why do you get absent synthesis alpha thalassaemia
deletion of both genes from chromsome 16
What is the most severe form of alpha thalassaemia?
HbH disease
only 1 working alpha gene per cell
What supplement do you need to give in alpha thalassaemia?
Folic acid (increased RNC turnover creates an increased demand)
How is beta thalassaemia usually caused?
Point mutation
How is beta thalassamia inherited?
Autosomal recessive
What is the diagnostic test for beta thalassaemia trait?
Raised HbA2
What does bet thalassaemia lead to if not diagnosed early?
Extramedullary haematopoiesis
How do you manage beta thalassaemia?
Regular transfusions to maintain the haemoglobin above 95g/L so as to suppress ineffective arythropoiesis and inhibit gut over absorption of iron.
What drugs are given in beta thalassaemia?
Iron
Iron cheleating drugs such as desferrioxamine
How is sickle cell anaemia inherited?
Autosomal recessive
What kind of mutation is seen in sickle cell anaemia?
Point mutation in codon 6 of the beta globin gene
How many abnormal genes do you have in sickle cell trait?
One
What are the precipitants of a sickle crisis?
Hypoxia Dehydration Infection Cold exposure Stress/Fatigue
What are the symptoms of sickle cell disease?
Tissue infarction due to vascular occlusion (symptoms dependent on site and severity)
- Digits
- Leg ulcers
- Sever pain
