ABNORMAL HEMOGLOBINS - DEFINITION , TYPES

 DEFINITION -

Mutations in the gene coding for globin chains affecting the formation and functioning of hemoglobin results in formation of abnormal hemoglobin's.

TYPES OF ABNORMAL HEMOGLOBIN'S

1.Hemoglobinopathies 

2.Thalassemias 

Hemoglobinopathies 

-- due to defect in the sequence of amino acids in the globin chain

--  Five major types

1.HbS - Sickle Cell Hemoglobin - replacement of glutamic acid at 6th position by valine in globin chain

2.HbC - Cooley's anemia - replacement of glutamic acid by lysine at 6th position in globin chain

3.HbE - replacement of glutamic acid by lysine at 26th position in globin chain

4.HbD - replacement of glutamic acid by glutamine at 121 position in globin chain

5.HbM- Methemoglobin - replacement of proximal/distal histidine by Tyrosine in globin chain

Thalassemia

-- due to defect in the rate of synthesis of globin chains

-- there is compensatory increase in other type of globin chains

Classification

I. On the basis of globin chains

-- α Thalassemias - decrease or total absence of rate of synthesis of α globin chains

-- β Thalassemia - decrease or total absence of rate of synthesis of β globin chains

II. On the basis of mode of inheritance -

-- Homozygous - α Thalassemia Major , β Thalassemia major

-- Heterozygous - α Thalassemia minor , β Thalassemia minor