Thalassaemia Flashcards
what is thalassaemia?
A haemoglobinopathy of the thalassaemia type meaning reduced or absent globin chains
what is alpha thalassaemia?
A thalassaemia leading to reduced/absent production of the alpha globin chains
what is beta thalassaemia?
A thalassaemia leading to reduced/absent production of the beta globin chains
what are the denotations used in thalassaemia?
(0)- absent production of the chain due to a mutation
(+)- reduced production due to a mutation.
what genes do we normally have for haemoglobin production?
4 alpha globin genes
2 beta globin genes
what is the inheritance pattern of thalassaemia?
autosomal recessive
what mutation most commonly leads to alpha thalassaemia?
Deletions- but a huge variety of mutations can cause alpha thalassaemia.
what are the types of alpha thalassaemia?
- Alpha thalassaemia minima (aa/a-)
- Alpha thalassaemia trait (a-/a-)
- Haemoglobin H disease (a-/–)
- Bart’s syndrome (–/–)
what are the symptoms of alpha thalassaemia minima (aa/a-)?
Asymptomatic often have normal MCV.
what is the management of alpha thalassaemia minima (aa/a-)?
No management needed.
what are the features of alpha thalassaemia trait (a-/a-)(aa/–)?
Asymptomatic or mild microcytic anaemia with a mild reduction in MCV.
what is the management of alpha thalassaemia trait (a-/a-)(aa/–)?
Often none needed
what is the condition where they have three abnormal alpha genes and one normal alpha genes?
Haemoglobin H disease
what are features of haemoglobin H disease (a-/–)?
Reduced red cell survival with a hypochromic microcytic anaemia
- pallor, anaemia, jaundice, hepatosplenomegaly, aplastic crisis and leg ulcers.
what are the key treatment options for haemoglobin H disease?
transfusions
iron chelation therapy with deferasirox if they get overload
folic acid supplements
splenectomy
what is haemoglobin barts disease (–/–)?
inheritance of four abnormal alpha genes which is incompatible with extrauterine life
why is barts disease often presenting in the first 6 months of life?
In Bart’s disease there are no alpha globin chains and these are needed for both HbA (normal Hb) and HbF (foetal haemoglobin).
what can babies develop in barts disease?
severe anaemia, high output cardiac faliure and oedema= hydrops fetalis.
what haemoglobin types are absent in barts disease?
No alpha chains due to all abnormal alpha genes. This leads to no HbA2, HbF and HbA.
what is the management of barts disease?
intrauterine transfusions, bone marrow transplants.
what is the only way to diagnose alpha thalassaemia minima or trait?
Genetic sequencing
how is alpha thalassaemia diagnosed?
Haemoglobin analysis with electrophoresis
what antenatal screening is in place for alpha thalassaemia?
Family origin questionnaire to determine further testing by week 10 gestation
what the investigation results in alpha thalassaemia?
FBC: low Hb, low MCV (Have microcytic anaemia)
Blood film: microcytic and hypochromic RBC’s
LFT’s: raised unconjugated bilirubinaemia (can cause pigmented gallstones and jaundice)
Haemolysis screen: raised lactate dehydrogenase, low haptoglobin.
Direct antiglobulin test (negative, non immune haemolysis)
what is beta thalassaemia?
Reduced or absent production of the beta globin chain
how many copies of the beta globin gene do we normally have?
2
what are the main forms of beta thalassaemia?
- beta thalassaemia minor/trait (b+/b or b0/b)
- beta thalassaemia intermedia (b+/b+)
- beta thalassaemia major (b+/b0 or b0/b0)
