Hemoglobinopathies Flashcards
Haemoglobin
Red oxygen carrying pigment
What does mean corpuscular haemoglobin show
Amount of Hb per RBC
What does mean corpuscular haemoglobin concentration show
Amount of Hb per unit volume
How many subunits in Hb
4 - tetramer
2 parts of Hb subunits
Haem
Globin
How many porphyrin rings in Haem
4
Which 6 atoms chelate iron in Haem
4 N
2 histidine
What is Hb metabolised to
Bilirubin
Products of alpha globin genes
Alpha globin chain
Zeta globin chain
Products of beta globin cluster genes
Epsilon globin
Gamma globin
Delta globin
Beta globin
Location of alpha globin gene cluster
Chromosome 16
Short arm position 13.3
How many functional genes in alpha globin gene cluster
3
Location of beta globin gene cluster
Chromosome 11
Short arm position 15.4
How many active genes in beta globin cluster
5
Which organs are Hb synthesised in in gestation
Yolk sac
Liver
Spleen
Where is Hb synthesised after birth
Bone marrow
When does the embryonic to foetal haemoglobin switch occur
6 wks gestation
Types of embryonic haemoglobin
Hb gower 1
Hb gower 2
Hb Portland
Which Hb is 2 zeta 2 epsilon
Gower 1
Which Hb is 2 alpha 2 epsilon
Gower 2
Which Hb is 2 zeta 2 gamma
Portland
Which subunits are in foetal haemoglobin
2 alpha 2 gamma
Where is HbF made
Liver
Spleen
When is HbF made
6 wks gestation - first few months after birth
Does adult or foetal Hb have a higher O2 affinity
HbF
When does HbA start being synthesised
40 wks gestation
Replaces HbF gradually at 3-6mo after birth
What globin chains are in HbA2
2 alpha 2 delta
Haemoglobinopathy
Group of genetic disorders involving the globin chains of the Hb complex
What are the 2 main groups of haemoglobinopathy
Abnormal globin structure
Abnormal globin production
What causes haemoglobinopathies
Mutations or deletions in globin genes
Which haemoglobinopathies cause abnormal globin chain production
Thalassaemias
Thalassaemia inheritance
Autosomal recessive
What does deletion of HbA1 and HbA2 genes cause
Alpha Thalassaemias
What do mutations in HBB genes cause
Beta Thalassaemias
4 types of alpha thalassaemia
Alpha thalassaemia major
Hb H disease
Alpha thalassaemia minor
Alpha thalassaemia minima
What genetic abnormality causes alpha thalassaemia major
Deletion of 4 alpha globin genes
Why is alpha thalassaemia major incompatible w life
No alpha globin synthesised so Hb contains Portland and non functional gamma tetramers (Hb Bart’s)
What is caused by deletion of 3 alpha genes
Hb H disease
What is haemoglobin H
Tetramer of beta globin formed in Hb H disease from excess beta globin
Which types of alpha thalassaemia cause Microcytic Hypochromic anaemia
Hb H disease
Alpha thalassaemia minor
What condition is caused by 2 missing alpha genes
Alpha thalassaemia minor
Which type of alpha thalassaemia creates normal Hb production and no symptoms
Alpha thalassaemia minima
What types of alpha Thalassaemias are carriers
Alpha thalassaemia minor
Alpha thalassaemia minima - silent carrier
Does beta thalassaemia have quantitative or qualitative effects on beta globin
Quantative
What happens to excess alpha globin subunits in beta thalassaemia
Forms insoluble aggregates
What are the 3 types of beta thalassaemia
Beta thalassaemia minor / trait
Beta thalassaemia intermediate
Beta thalassaemia major
How does beta thalassaemia cause anaemia
Ineffective erythropoiesis and haemolysis due to excess alpha chain precipitates
Where do excess alpha chains precipitate in beta thalassaemia
RBCs
RBC precursors
Effects of beta thalasssaemia
Ineffective erythropoiesis
Haemolysis
Bone marrow expansion
Increase GI iron absorption
How does thalassaemia effect MCV
Decrease
How does thalassaemia effect serum iron, serum ferritin, tibc, and bone marrow iron
No effect
Are RBCs macro micro or Normocytic in Thalassaemia
Microcytic
Thalassaemia treatment
Regular blood transfusions
Iron chelation therapy
Splenectomy
Allergenic bone marrow transplant
Which amino acids are switched in haemoglobin s
Hydrophilic glutamic acid replaced by hydrophobic valine
Which codon is GAG replaced by in haemoglobin s
GTG
How is sickle cell anaemia inherited
Autosomal recessive
Why does Hb S polymerise
Hydrophobic section created by substituted valine sticks to hydrophobic region on adjacent Hb
Does sickle cell anaemia effect beta or alpha globin
Beta
Which position on beta globin does the substitution occur in HbS
6
What causes RBC membrane damage in sickle cell anaemia
Repeated sickling and unsickling between normal shaped oxy state and sickled deoxy state
Vasoocclusive crises
Sickle cells obstruct capillaries and restrict blood flow to an organ causing ischaemia, pain, and organ damage
What causes haemolytic anaemia, and jaundice in sickle cell anaemia
Destruction of sickled RBCs
Consequences of sickle cell disease
Haemolytic anaemia
Increased infection susceptibility
Vaso occlusive crises
Chronic tissue damage
Sickle cell disease management
Antibiotic prophylaxis
Analgesics for vasoocclusive crises
Blood transfusions
Hydroxyurea
Bone marrow transplants
Why are antibiotics used prophylactically in SCD
Infection increases O2 demand, increasing vasooclusive crises
How does hydroxyurea help SCD
Increases HbF
Reduces crises