08-08-2012, 11:28 AM
THALESSEMIA
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Thalassemia is a group of inherited disorders that affects the amount and type of haemoglobin a person produces. Haemoglobin helps red blood cells spread oxygen through your body. Low levels of haemoglobin may cause anaemia. A haemoglobin molecule is made up of heme, an iron-containing complex, globin, protein chains that surround the heme. The types of protein chains found in the haemoglobin molecule affect its structure and function. Severe anaemia can damage organs and lead to death.
causes
It is passed from parent to child. A defect in one or more genes causes it. Both parents must carry a gene for the disease in order to pass it to their child.
CLASSIFICATION
There are two main types: α & ß. Beta thalassemia is the most common.
Beta thalassemiaBoth alpha and beta-globin are needed to make haemoglobin.
Beta thalassemia occurs when one or both of the two genes that make beta-globin don't work or only partly work as they should. Beta thalassemia’s are due to mutations in the HBB gene on chromosome 11
If one damaged geneàmay have mild anaemia and don't need treatment. This is called beta thalassemia minor or beta thalassemia trait. It happens when the individual gets a normal gene from one parent and a thalassemia gene from the other.
When both genes are damaged, it means individual has got a thalassemia gene from each parent. May have moderate or severe anaemia.
Moderate anaemia (beta thalassemia intermedia),à need blood transfusions. Extreme activity of the bone marrow produces bone deformities of the face and other areas, along with enlargement of the spleen. The patient has thalassemia that is more severe than thalassemia trait, but not so severe as to require chronic transfusion as do the patients with thalassemia major.
Severe anaemia (called beta thalassemia major or Cooley's anaemia)à needs chronic blood transfusions throughout life. Symptoms of anaemia usually begin within a few months after birth. In some patients the anaemia is so severe, that death occurs without transfusions. Other patients could survive without transfusions, for a while, but would have terrible deformities. While transfusions are life-saving in patients with thalassemia major, transfusions ultimately produce iron overload. Chelation therapy, usually with the iron-binding agentàDesferal, is needed to prevent death from iron-mediated organ injury.
Alpha thalassemia
It is due to a deletion or mutation in one or more of the four alpha globin gene copies. The α thalassemia’s involve the genes HBA1 and HBA2
The more genes affected, the less alpha globin produced.
Silent Carrier State (1 affected gene): one gene is missing or damaged: no symptoms and don’t need treatment. But the individual is a silent carrier. This means individual doesn't have the disease but can pass the defective gene to the child.
Alpha Thalassemia Trait: two genes are missing or damaged: patient will have very mild anaemia that will not need treatment. This is called alpha thalassemia minor or alpha thalassemia trait.
Hemoglobin H Disease : three genes are missing: patient will have mild to moderately severe anaemia. This is sometimes called haemoglobin H disease. If severeàneed blood transfusions. These patients typically have enlarged spleens. The bone marrow works at an extraordinary pace in an attempt to compensate for the anaemia. As a result, the marrow cavity within the bones is stuffed with red cell precursorsàcause the bone to "mold" and flair out. Patients with haemoglobin H disease also develop large spleens. The spleen has blood forming cellsà these cells become hyperactive and over expand àresult is a spleen that is often ten-times larger than normal. Patients with haemoglobin H disease often are small and appear malnourished, despite good food intake.