sickling disorders Flashcards
what is it?
- Point mutation in codon 6 and the B globin gene that substitutes glutamine to valine producing Bs
- This alters the structure of the resulting Hb→ HbS (α2βs2)
- HbS polymerises if exposed to low oxygen levels for a prolonged period
- This distorts the red cell, damaging the RBC membrane
what is sickle cell trait (HbAS)
- One normal, one abnormal B gene
- Blood film normal
- Mainly HbA, HbS <50%
how does sickle cell trait present
- Asymptomatic carrier state – 300 million carriers worldwide
- Few clinical features as HbS level too low to polymerise
- May sickle in severe hypoxia eg high altitude, under anaesthesia
what is sickle cell disease?
Compound heterozygosity for HbS and another β chain mutation, for example:
o HbS/β thalassaemia
o HbSC disease; milder, but increased risk of thrombosis
what is sickle cell anaemia?
Two abnormal β genes (βs/βs)
HbS > 80%, no HbA
what is a sickle crisis?
Sickle vaso-occlusion – results in tissue ischaemia and pain (episodes of tissue infarction)
- symptoms are dependent on site and severity
what are some of the pathophysiology/ effect on the body of sickle cell anaemia?
Chronic haemolysis – shortened RBC lifespan
• Sequestration of sickled RBCs in liver and spleen
• Hyposplenism due to repeated splenic infarcts
what is Ellie’s birthday?
6th June
what precipitates a sickle crisis?
- Hypoxia
- Dehydration
- Infection
- Cold exposure
- Stress/fatigue
how do you manage a sickle crisis?
- Opiate analgesia
- Hydration
- Rest
- Oxygen
- Antibiotics if evidence of infection
- Red cell exchange transfusion in severe crisis eg (lung) chest crisis or (brain) stroke
what is the longterm management of sickle cell anaemia?
Hyposplenism - reduce risk of infection
o prophylactic penicillin
o vaccination; pneumococcus, meningococcus, haemophilus
Folic acid supplementation (↑ RBC turnover so ↑demand)
Hydroxycarbamide can reduce severity of disease by inducing HbF production
Regular transfusion to prevent stroke in selected cases
