Hemoglobinopathies Flashcards
(15 cards)
What is the role of globin chains in a haemoglobin molecule
Keeps heme soluble
Protects heme from oxidation
List the major forms of haemoglobin
- HbA - 2 alpha 2 beta
- HbA2 - 2 alpha 2 delta
- HbF - 2 alpha 2 gamma
Which is the most clinically relevant form of Hb?
HbA - major form present in adults
Which globin genes are found on chromosome 16?
alpha like genes
Two per chromosome (4 per cell)
Which globin genes found on chromosome 11?
Beta like genes
one beta per chromosome (2 per cell)
The expression of globin chains is permanent - T/F?
F
Expression of globin genes changes during embryonic life and childhood
What are haemoglobinopathies?
Hereditary conditions affecting GLOBIN change synthesis
What pattern of inheritance do hemoglobinopathies follow?
Autosomal recessive
What are the two main groups of haemoglobinopathies
Thalassemia - decr. rate of normal globin chain synthesis
Structural Hb variants - normal production of abnormal globin chain (variant haemoglobin)
What is thalassemia?
Reduced globin chain synthesis leading to impaired Hb production
Which thalassemia affects alpha chains?
Alpha thalassemia
Which thalassemia affects beta chains?
beta thalassemia
What are the consequences of thalassemia?
Inadequate Hb - microcytic, hypochromic anaemia
If severe:
a) unbalanced accumulation of globin chains - toxic to the cell
b) Haemolysis
c) Ineffective erythropoiesis
What is the pathophysiology of alpha thalassemia?
Inherit two copies of alpha genes from each parent
If you either inherit <2 or none from parents on chromosome 16, you will have reduced or absent alpha chain synthesis
Since alpha chains present in HbA, HbA2 and HbF all are affected
Classification of alpha thalassemia
Based on number of alpha genes
Unaffected = 4 normal α genes (αα/αα)
α thalassaemia trait; one or two alpha genes missing
HbH disease; only one alpha gene left (–/-α )
Hb Barts hydrops fetalis; no functional α genes (–/–)
