Haemolyticanaemia

Haemolyticanaemia
Genetic disorders of hemoglobin:
These are inherited diseases caused by reduced or abnormal synthesis of globin chains.
Hemoglobin synthesis:
The main function of hemoglobin is to carry O2 to the tissue and to return carbon dioxide(CO2) from the tissue to the lungs ,in order to achieve this gaseous exchange they contain specialized protein hemoglobin, each molecule of normal adult hemoglobin (Hb A) consists of four polypeptide chains ?2?2 each with its own haem group.Normal adult blood also contain small quantities of two other haemoglobins: Hb F and HbA2.These also contain ? chains but with ? and ? chain respectively instead of ? chains.

Normal hemoglobin in adult blood:
Hb A Hb F Hb A2
Structure (globin chains) ?2?2 ?2?2 ?2?2
Normal (%) 96-98 0.5-0.8 1.5-3.2

Haemoglobin F is the predominant Hb in fetal and neonatal life, the major switch from fetal to adult Hb occurs 3-6 months after birth .
Hemoglobin abnormalities
These result from the following:
1-reduced rate of synthesis of normal ? or ? globin chains(the? and ? thalasemias).
2-synthesis of an abnormal Hb(HB S).
The genetic defect of haemoglobin are the most common genetic disorder world wide,? thalasemias is more common in the Mediterranean region ,while ? thalasemias is more common in the far east.