Sickle cell disease is an autosomal recessive condition caused by an abnormal form of haemoglobin, HbS, which polymerises into long crystals when it deoxygenates, resulting in the sickling of red blood cells. This abnormality is caused by a glutamine to valine substitution on the beta globin chain.
- HbSS = sickle cell anaemia = commonest form in UK and most severe
- HbSC = SC disease = mild anaemia
- HbS beta thalassaemia trait
Carriers are asymptomatic and have increased resistance to malaria.
Diagnosis of sickle cell disease is by electrophoresis.
Complications of sickle cell disease include:
- Simple pain crisis
- Sequestatration crisis
- Acute chest syndrome
- Breathlessness, chest/back pain, fever, cough
- Possible causes include sequestatration, infection and pulmonary vascular occlusion
- Splenic sequestration
- Eventualy spleen becomes atrophic --> increased risk of infection
- Aplastic crisis
- Classically due to parvovirus
- Haemolytic anaemia
- Priapism – up to 8% of male patients
- Avascular necrosis of the hip
- Renal failure – up to 5%
- Eye problems
- Retinal detachment
- Pulmonary hypertension
- Iron overload (due to recurrent transfusions)
Precipitants of a sickle cell crisis:
- Blood must be matched for minor blood group antigens Kell and Rh
- Increases production of HbF
- Prophylactic antibiotics
- Acute pain management: Oral/IV analgesia as per pain ladder; morphine/diamorphine/PCA may be needed
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Piel, F. et al. Global distribution of the sickle cell gene and geographical confirmation of the malaria hypothesis. Nat Commun. 2010; 1:104.