Normal Haemoglobin is essential for carrying oxygen in human body.Thalassaemia, the most common inherited single gene disorder in the world, are a diverse group of genetic blood diseases characterised by absent or decreased production of normal haemoglobin, resulting in anaemia of varying degree.
What causes thalassaemia?
It is caused by a mutation or deletion of the genes that control one or more of 4 globin chain production.This leads to decreased synthesis of haemoglobin and clinical manifestation of thalassaemia.The quantity and properties of normal globin chain aggregates determine the characteristics and severity of the thalassaemia.
How is thalassaemia inherited?
A child inherits haemoglobin genes from both parents.For example, if both parents have beta thalassaemia trait, there is: a 1 in 4 chance of the child having normal haemoglobin genes; a 1 in 2 chance of the child having beta thalassaemia minor; and a 1 in 4 chance the child will have beta thalassaemia major or intermedia.
What are the different types of thalassaemia?
The main types of thalassaemia are called alpha thalassaemia and beta thalassaemia.(The alpha and beta refer to which haemoglobin gene is affected, and which of the haemoglobin chains is faulty.) There are some rarer types too.
Thalassaemia minor is a mild form of Thalassaemia minor often mistaken for iron deficiency anaemia.It occurs when one of four globin chain is affected.It can be either alpha of beta type. Your blood count may be a little lower than other people of your age and sex, but this produces no symptoms.You were born with this condition and you will have it all of your lifetime. If you marry a person who does not have Thalassaemia Minor, your children may have Thalassaemia Minor. If you marry a person who does have Thalassaemia Minor, some of your children may have Thalassaemia Major. There is no need for treatment and most people who have inherited this are not sick.
Beta Thalassaemia Major occurs when a person inherits two Thalassaemia genes, one from each parent.Both parents must have Thalassaemia Minor.When two individuals who have beta Thalassaemia Minor marries, there is a 25% chance that any pregnancy can result in a child with Thalassaemia Major. Two of four children will have Thalassaemia Minor, and one of four will be normal. These chances are present with each pregnancy. Some families have had only one ill child, while others have had all of their children affected.The double dose of two Thalassaemia genes causes an anaemia that is so severe that regular blood transfusions must be given throughout life, starting from age of 6-9 months. As they grow, infants with Thalassaemia Major exhibit paleness and fussiness. Weakness and slow growth appear in the first or second years of life. The abdomen may swell due to an enlarged liver and spleen. Changes occur in the appearance of the face and head.The eyes appear slanted and the cheekbones become prominent.
Excessive iron get deposited in organs like liver, heart, pancreas, gonadal organs etc., leading to progressive dysfunction of these organs over period of years of repeated blood transfusions.
Beta Thalassaemia intermedia, as name suggests, are less severe than thalassaemia major, occurs when one has genetic defect same as minor but clinical they are similar to thlassaemia major which is starting little later in life, e.g., 7 years or so when they require blood transfusion. These patients may also become blood transfusion dependent and have side effects of excessive blood transfusion like thalassaemia major.
Hb H disease is a type of alpha thalassaemia, due to having three missing alpha haemoglobin genes (normally each person has four of these genes). This can happen if one parent has alpha plus thalassaemia and the other has alpha zero thalassaemia.It usually causes a mild but persistent anaemia. Sometimes Hb H causes more symptoms and is similar to beta thalassaemia intermedia.
Hb Barts is the most severe form of thalassaemia, where all the alpha haemoglobin genes are abnormal or missing. It occurs if a baby inherits two alpha zero thalassaemia genes. In this condition, no normal haemoglobin can be made, even before birth. It is the most serious form of thalassaemia - so serious that the baby will usually die in the womb from severe anaemia.
Sickle Cell/Beta Thalassaemia can occur if one parent has a beta thalassaemia gene, and the other parent carries a gene for a different haemoglobin disorder called sickle cell anaemia. If their child inherits one of each gene, the combination is called sickle cell/beta thalassaemia - also called 'sickle cell disease'. This condition behaves like sickle cell anaemia (not like thalassaemia) and is treated in the same way as sickle cell anaemia.
How is thalassaemia diagnosed?
The diagnosis is made by a blood test. Beta thalassaemia can diagnose on test called HPLC (High Performance Liquid Chromatography) showing different characteristic patterns. This is done on patient and their parents. In some cases, extra tests, such as DNA (genetic) tests are needed to diagnose the exact type of thalassaemia.
Alpha thalassaemia is diagnosed from molecular gene test from blood.
How thalassemia is diagnosed prenatal in pregnant ladies?
A prenatal test (on the unborn baby) can be done from 10 weeks of pregnancy onwards, depending on the type of test used. The usual tests offered are Chorionic Villus Sampling (CVS) or amniocentesis. It involves ultrasound guided aspiration of fetal sample for testing for thalassaemia.
If you have previous child with thalassaemia major, or both the partners are thalassaemia minor, prenatal testing is advised as thalassemia major birth best prevented.
What is treatment of thalassaemia?
Treatment involves regular blood transfusions that must be given every 4 to 6 to maintain pre-transfusion haemoglobin level of 9 g/dl. Complications that may arise from regular blood transfusions include an overload of iron build up in vital organs causing diabetes, liver disease and heart failure.Blood transfusion reactions and allo-immunisation due to repeated transfusion are leukoreduced by using pre-storage leukodepletion (preferred) or by using bedside leukocyte filter.
The spleen may become so enlarged or overactive causing abdominal discomfort due to size and can lead to increased blood transfusion frequency. It is called hypersplenism. Once this complication occurs it has to be removed by surgery called splectomy.
Iron overload can be controlled with regular medications reducing iron level. It is called iron chelation. It is done with injections of Desferal or nowadays with oral drug called Deferasirox (Asunra/Defrijet).Deferasirox is available as oral drug and is very convenient and effective for controlling this important complication.It needs to be started early in life and taking it regularly with monitoring of liver, kidney function along dose adjustment with periodic assessment with blood test- ferritin or sometimes with MRI of liver/ heart when organ dysfunction is suspected.
Bone Marrow Transplant from HLA matched sibling is the only curative therapy for thalassemia. Best results of 80-85% are achievable if done early in the course of disease before complications set in.With the available transplant centres and experts in India, this has become most cost effective way of treating thalassaemia major.
Prenatal fetal testing while mother with thalassaemia is pregnant is crucial to prevent baby birth from this disease.
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