Thalasemia

What is Thalassemia

The thalassemia gene may be maintained in the human population, in part because of the greater immunity of heterozygous individuals against malaria and is found in parts of the world where malaria is common

These include Southeast Asia, China, India, Africa, and parts of the Mediterranean.
TYPES OF THALASSEMIA

Hemoglobin is made of two proteins: Alpha globin and beta globin. Thalassemia occurs when there is a defect in a gene that helps control production of one of these proteins.

There are two main types of thalassemia:
A) Alpha Thalassemia
B) Beta Thalassemia
c) Delta Thalassemia
Alpha Thalassemia
Alpha thalassemia occurs when a gene or genes related to the alpha globin protein are missing or changed (mutated)
The α thalassemia involve the genes HBA1 and HBA2.Mutation of 1 or more of the 4 alpha globin genes on chromosome 16.
severity of disease depends on number of genes affected
Results in an excess of beta globins.
The excess β chains form unstable tetramers (called Hemoglobin H or HbH of 4 beta chains), which have abnormal oxygen dissociation curves.
Alpha Thalassemia Trait
2 functional globin genes
Results in smaller blood cells that are lighter in colour.
No serious symptoms, except slight anemia
Beta Thalassemia
Beta thalassemia occurs when similar gene defects affect production of the beta globin protein.

Beta thalassemia are due to mutations in the HBB gene on chromosome 11 , also inherited in an autosomal-recessive fashion. The severity of the disease depends on the nature of the mutation.

Hundreds of mutations possible in the beta globin gene, therefore beta thalassemia is more diverse

Results in excess of alpha globins.
Beta Thalassemia Trait


Slight lack of beta globin

Smaller red blood cells that are lighter in colour due to lack of hemoglobin

No major symptoms except slight anemia
Beta Thalassemia Intermedia
lack of beta globin is more significant

bony deformities due to bone marrow trying to make more blood cells to replace defective ones

causes late development, exercise intolerance, and high levels of iron in blood due to reabsorption in the GI tract



Persons with thalassemia minor have (at most) mild anemia (with slight lowering of the hemoglobin level in the blood). This situation can very closely resemble that with mild iron-deficiency anemia.

However, persons with thalassemia minor have a normal blood iron level (unless they have are iron deficient for other reasons). No treatment is necessary for thalassemia minor. In particular, iron is neither necessary nor advised.

Delta Thalassemia
As well as alpha and beta chains present in hemoglobin, about 3% of adult hemoglobin is made of alpha and delta chains. Just as with beta thalassemia, mutations that affect the ability of this gene to produce delta chains can occur.


Problem in formation of delta chain can cause this type of thalassemia.
How is the disease transmitted?
All forms of thalassemia are inherited. The disease cannot be caught from another person who has it.

Thalassemia is passed on through parents who carry the thalassemia genes in their cells.

When both parents carry Alpha thalassemia genes, any child that they have is at risk for inheriting a more severe form of this condition.

Individuals who know they have one of these disorders, and those from countries where they are common should consider consulting a genetic counselor to find out whether their child could be at risk.
Test & Investigation of Thalassemia


Solubility testing-Dithionite tube test
Alkali denaturation test for quantification of fetal hemoglobin
Acid elution test for fetal hemoglobin distribution
Unstable hemoglobin testing for Heinz bodies.
Hemoglobin electrophoresis
Major test for identifying thalassemia and hemoglobinopathy Types
Cellulose acetate: Alkaline pH
Citrate agar: Acid ph

Symptoms of Thalassemia
The most severe form of alpha thalassemia major causes stillbirth (death of the unborn baby during birth or the late stages of pregnancy)

Treatment
Mild thalassemia : patients with thalassemia traits do not require medical or follow-up care after the initial diagnosis is made. Patients with β-thalassemia trait should be warned that their blood picture resembles iron deficiency and can be misdiagnosed. They should eschew empirical use of Iron therapy; yet iron deficiency can develop during pregnancy or from chronic bleeding.Counseling is indicated in all persons with genetic disorders, especially when the family is at risk of a severe form of disease that may be prevented.

Severe thalassemia : patients with severe thalassemia require medical treatment, and a blood transfusion regimen was the first measure effective in prolonging life.
More Permanent Treatment Options

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