Treatment for Thalasseamia Major
Blood Transfusions – 2-3 weekly transfusions. These transfusions eliminate the complications of anemia and compensatory bone marrow expansion. Frequent transfusions result in an inexorable accumulation of tissue iron, if this iron is not removed the consequence is fatal. Deferoxamine mesylate is used as an iron-chelating agent that binds to the excess iron and is excreted through the urine and faeses. Chelators are administered orally, intramuscularly or intravenously and are required daily. The injections take approximately 10 hours and the infusion pump is generally worn overnight.
Tablet - deferasirox
Splenectomy – if the patients yearly transfusion requirements exceed 200ml packed cells per kilogram body weight, the removal of the spleen significantly diminishes red blood cell requirements and iron accumulation. Hypersplenism may be avoided by early and regular transfusion.
Bone Marrow Transplant – replacing affected bone marrow with healthy donated bone marrow, which will begin producing healthy blood cells.
Cord Blood Transfusion – involves testing the Human Lymphocyte Antigen (HLA) type of a foetus that does not have thalasseamia, carried by a mother than has a child with thalasseamia. If the HLA of the foetus matches that of the older sibling, it is possible to take a sample of blood from the foetus’s umbilical cord that can be used for transfusion. The blood is known as cord blood, and it is useful because it is a rich source of stem cells. These cells can be used instead of bone marrow because they are also capable of producing
sources - www.bloodjournal.org
- http://www.nhsdirect.nhs.uk
- www.gsnv.org.au/pages/supportGroups/tsv
- www.health-care-articles.info/diseases/thalassaemia
Thursday, April 10, 2008
Wednesday, April 9, 2008
Incidence of Thalassaemia
Incidence of Thalassaemia
PCL 6 – Swee Lan gets clucky
Amber Hartley
Thalassaemia is particularly common in people from the Mediterranean, Africa and southeast Asia. Incidence can be as high as 1/10 in some Mediterranean areas.
PCL 6 – Swee Lan gets clucky
Amber Hartley
Thalassaemia is particularly common in people from the Mediterranean, Africa and southeast Asia. Incidence can be as high as 1/10 in some Mediterranean areas.
The above image, taken from http://www.gpgenetics.edu.au/12/12_index.html, depicts the global distribution of haemoglobinopathies. This is not just Thalassaemia incidence, but includes other haemoglobinopathies including Sickle Cell Anaemia.
The WHO estimates that, on a global scale, at least 5% of adults are carriers for a haemoglobinopathy. Approximately 2.9% of people, globally, are carriers for thalassaemia.
Incidence and carrier rates of Thalassaemia are different in each country, largely because populations have different ethnic origins.
Prevalence of β Thalassaemia
Particular sub-groups at increased risk of being a carrier for β-thalassaemia are those from the Middle East, Southern Europe, India, Central and Southeast Asia, and Africa. In some regions, 1 in 5 people may carry a β-thalassaemia mutation.
Prevalence of α Thalassaemia
Those most commonly at risk of α-thalassaemia are from China or Southeast Asia, but people from Southern Europe, the Middle East, India, Pakistan, Africa, the Pacific Islands, New Zealand (Maori), and some Indigenous Australia communities are also at higher risk.
In general, people with a family history of thalassaemia, or a history of severe pre-eclampsia associated with early fetal death, are also at higher risk.
References
Genetics in Family Medicine, “Haemoglobinopathies.” http://www.gpgenetics.edu.au/12/12_index.html, 2007
World Health Organisation, “Data and Statistics.” http://www.who.int/research/en/ 2008
Tuesday, April 8, 2008
Genetics of Thalassaemia
Thalassaemia is a genetic disease brought about by the inheritance of faulty genes that code for protein chains making up the haemoglobin protein found in red blood cells. Haemoglobin is made up of four protein chains – two ‘alpha’ (α) globin chains and two ‘beta’ (β) globin chains. Defects in certain genes coding for alpha or beta chains can result in various forms of alpha or beta thalassaemia, depending on which chain is affected. These conditions are classified under the umbrella term haemoglobinopathies. The pattern of inheritance of these genes is autosomal recessive.
Two identical α-globin genes exist on chromosome 16, coding for the alpha chains. Since each person inherits a pair of chromosomes (one from each parent), every person would have four copies of each gene.
Carrier states
- When only one α-globin gene is faulty, the thalassaemia that results does not affect the person, as there are still sufficient mounts of alpha chains are produced by cells. A person with this condition would be known as a silent carrier
- When two faulty α-globin genes are inherited, the carrier may suffer from mild anaemia, but are generally healthy. If the two faulty genes occur on the same chromosome, it is known as alpha zero trait. If they occur at the same loci, it is known as alpha plus trait.
Affected states
- The inheritance of three faulty α-globin genes results in an intermediate form of thalassaemia known as haemoglobin H disease, of HbH. The patient would usually suffer life-long anaemia.
- When all four faulty α-globin genes are inherited, the condition, known as Hb Barts hydrops fetalis, or Alpha thalassaemia major, is fatal to all affected babies, who die soon after birth.
Since there is only one β-globin gene on chromosome 11, every person would inherit two copies of this gene.
- Those with the beta thalassaemia minor condition inherit one faulty β-globin gene, and suffer only from mild anaemia i.e. carrier status
- Beta thalassaemia major suffers have two faulty β-globin genes, and can experience severe anaemia. This condition is also known as Cooley anaemia.
With beta thalassaemia, due to only one gene controlling the production of β-globin chains, inheritance follows an autosomal recessive pattern. For example, a couple who are both carriers of the beta thalassaemia trait will have a 25% chance of having a non-carrier child, 50% chance of having a child who’s a carrier, and a 25% chance of a child with beta thalassaemia major.
The inheritance pattern is slightly more difficult with alpha thalassaemia, due to there being four alpha globin gene copies. However, if one assumes that crossing over doesn’t occur at the α-globin loci, a couple who both posses the alpha zero trait would have a 25% chance of having a child with all four α-globin gene copies, a 50% chance of a child with alpha zero trait, and a 25% of a child with alpha thalassaemia major (Hb Barts hydrops fetalis).
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