Anemia and Thalassemia

Anemia

Anemia (a-NE¯-me¯-a) is a condition in which the oxygen-carrying capacity of blood is reduced. All of the many types of anemia are characterized by reduced numbers of RBCs or a decreased amount of hemoglobin in the blood. The person feels fatigued and is intolerant of

cold, both of which are related to lack of oxygen needed for ATP and heat production. Also, the skin appears pale, due to the low content

of red-colored hemoglobin circulating in skin blood vessels. Among the most important causes and types of anemia are the following:

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• Inadequate absorption of iron, excessive loss of iron, increased iron

requirement, or insufficient intake of iron causes iron-deficiency anemia, the most common type of anemia. Women are at greater risk for iron-deficiency anemia due to menstrual blood losses and increased iron demands of the growing fetus during pregnancy.

Gastrointestinal losses, such as those that occur with malignancy or

ulceration, also contribute to this type of anemia.

• Inadequate intake of vitamin B12 or folic acid causes megaloblastic

anemia, in which red bone marrow produces large, abnormal red blood cells (megaloblasts). It may also be caused by drugs that alter gastric secretion or are used to treat cancer.

• Insufficient hemopoiesis resulting from an inability of the stomach

to produce intrinsic factor, which is needed for absorption of vitamin B12 in the small intestine, causes pernicious anemia.

• Excessive loss of RBCs through bleeding resulting from large

wounds, stomach ulcers, or especially heavy menstruation leads to

hemorrhagic anemia.

• RBC plasma membranes rupture prematurely in hemolytic anemia. The released hemoglobin pours into the plasma and may damage the filtering units (glomeruli) in the kidneys. The condition may result from inherited defects such as abnormal red blood

cell enzymes, or from outside agents such as parasites, toxins, or

antibodies from incompatible transfused blood.

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• Deficient synthesis of hemoglobin occurs in thalassemia , a group of hereditary hemolytic anemias. The RBCs are small (microcytic), pale (hypochromic), and short-lived. Thalassemia occurs primarily in populations from countries bordering the Mediterranean Sea.

• Destruction of red bone marrow results in aplastic anemia. It is

caused by toxins, gamma radiation, and certain medications that inhibit enzymes needed for hemopoiesis.

 Thalassemia :

(1) Thalassemia is an autosomal recessive disorder. The synthesis of alpha chains are controlled by two genes , ( HBA1 and HBA2 ) on chromosome 16. Beta chain synthesis is controlled by gene HBB located on chromosome 11. Two alpha chains and two beta chains together form four polypeptide chains that make heterotetrameric haemoglobin molecule . But when there is a defective gene on either of chromosome 16 or 11 , there is quantitative abnormality of polypeptide globin chain synthesis . This results into thalassemia.  

( 2 ) Depending upon which chain is affected , thalassemia is classified as , alpha ( x ) thalassemia and beta ( B ) thalassemia .

( 3 ) The clinical symptoms of thalassemia are as follows : 

( 1 ) Pale yellow skin . 

( ii ) Anaemia due to inability to synthesize haemoglobin . 

( iii ) Slow growth and development . 

( iv ) Variation in the shape and size of RBCs . 

( 4 ) Patients need regular blood transfusions to cope with the disorder .