Sickle Cell Anaemia and Thalassaemia Flashcards
What is sickle cell disease?
It is a autosomal recessive disease which causes RBC’s to be sickle shaped and have a reduced life span.
The reduced life span is exacerbated by low oxygen tension, dehydration and the cold.
What are the different classifications of sickle cell disease?
Homozygote for beta S global aka suffers from Sickle cell anaemia, this is the most severe form.
Heterozygote HbA and HbS aka a carrier this is protective against malaria.
Someone can also be heterozygote HbS and HbC. C is another abnormal haemoglobin gene which can be inherited. They will suffer from some disease.
Can also be a carrier of varying degrees of thalassemia + beta S global which can give similar pictures to sickle cell anaemia..
What are the signs and symptoms of sickle cell disease?
In the most severe form HbSS:
Anaemia of ~6 there will be malaise and potential breathlessness associated
May be haemolytic jaundice. Note may have splenomegaly in young children.
Increase incidence of infection (pneumococcal) due to hyposplenism due to infarcts (sickle celled rbc more likely to occlude vasculature)
Painful crises due vaso-occlusive episodes often in the hand and feet.
Priapism
What are the long term complications of sickle cell disease?
- Short stature and delayed puberty
- Stroke and cognitive problems
- Adenotonsillar hypertrophy
- Cardiac enlargement – from chronic anaemia
- Heart failure – from uncorrected anaemia
• Renal dysfunction
How is sickle cell disease managed?
Full immunisation.
Prophylactic daily oral penicillin throughout childhood.
Folic Acid supplementation.
Vaso-occlusive crises should be avoided by avoiding the:
- cold
- dehydration
- exercising excessively
- undue stress
- hypoxia.
Treatment of an acute crises should be analgesia and good hydration with oxygen if needed.
What is the prognosis of sickle cell anaemia?
3% die during childhood from infection.
Around 50% of patients with the most severe form will die before 40.
What is the screening test that is performed for sickle cell anaemia and other haemaglobinopathies?
Guthrie test performed in the neonatal period.
What is thalassemia?
Thalassemia is an autosomal recessively inherited haemaglobinopathy.
There are 2 forms beta and alpha.
Describe the pathophysiology of alpha and B-thalassaemia?
Alpha thalassaemia:
Healthy individuals have 4 alpha global genes. If all 4 are deleted then the individual will not be able to produce alpha global chains. This is known as alpha thalassaemia major which is not compatible with human life.
If there are 3 deletions and 1 functioning gene then the anaemia will be mild-moderate.
If there are 1 or 2 deletions the individual will be an asymptomatic carrier.
In B-thalassaemia due to abnormal genes the body cannot produce adequate amounts of B-globin chains, there is therefore a reduction in HbA (2 alpha and 2 beta).
All affected individuals have a severe reduction in B-globin and disease severity depends on the amount of residual HbA and HbF production.
What are the different variants of B-thalassaemia?
B-thalassaemia major – this is the most severe form of the disease. HbA (alpha 2, beta 2) cannot be produced because of the abnormal B-globin gene.
B-thallassaemia intermedia - is a similar but less severe form of the disease in which small amounts of normal Hb (HbA) can be produced or in which large amounts of HbF can be produced.
What are the signs and symptoms of B-thallassemia?
Profound anaemia with associated symptoms.
Stunted growth.
Haemolytic anaemia
Hepatosplenomegaly and bone marrow expansion (if not treated)
How do you treat B-thalassaemia?
Fatal without treatment.
Lifelong monthly blood transfusions aiming to keep Hb above 100 and to prevent bone malformation and poor growth.
Repeat transfusions can cause chronic iron overload which can cause cardiac failure, liver cirrhosis, diabetes, infertility and growth failure.
Therefore all patients are treated with iron chelation from the age of 2-3 years.
An alternative option is bone marrow transplant which is curative. This is reserved for patients with a compatible sibling where there is a 95% chance of success.
What is the prognosis in thalassemia?
90% chance of reaching 40 years.
