Sickle Cell and Thalassaemia (OSMOSIS) Flashcards
Because Barbara's lectures are so awful
What is sickle cell anaemia?
Homozygous for HbS
What is sickle cell trait?
Heterozygous for HbS
What is the benefit of sickle cell trait?
Protects against malaria (P falciparum)
What is normal HbA made up of?
2 alpha and 2 beta chains
Each chain carries a heme molecule
How is HbS transmitted vertically?
Autosomal RECESSIVE
What does the mutation in sickle cell anaemia comprise of?
Substitution with VALINE
instead of glutamic acid
Valine is hydrophobic and mutates the beta globin chain
What is HbS made up of?
2 alpha + 2 mutated beta globin chains (+ heme)
What happens when HbS is de-oxygenated?
It changes shape, so it agglutinates with other HbS > forms long polymers that transform RBC got sickle
What is the process that leads to RBC destruction in SCD?
Repeated sickling > weakened RBC membrane > premature RBC destruction with intravascular haemolusis
What are consequences of intravascular haemolysis?
Consequences of intravascular haemolysis:
- anaemia
- decreased free haptoglobin > unconjugated bilirubin > jaundice
What are symptoms of sickle cell disease
Sickle cells stuck in capillaries
- dactillitis
- pain crisis, avascular necrosis
- renal necrosis
- acute chest syndrome
- stroke
- splenic infarct, sequestration > hyposplenism
What occurs as a consequence to hyposplenism in SCD?
Patients become susceptible to encapsulated bacteria e.g. strep pneumoniae, H influenza, N meningitides, Salmonella
What are typical blood cells visible on smear for sickle?
HOWELL JOLLY BODIES
What is alpha thalassaemia?
Deficiency in production of alpha globin chains of HbA
How are alpha chain mutations transmitted vertically?
Autosomal RECESSIVE
