predictive factors of severity in sickle cell disease (SCD)

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The level to which SCD clinically manifests itself can vary significantly:

  • HbSS and HbS/ beta thalassaemia display greatest severity
  • severity of sickling depends on the percentage of haemoglobin present

Several genetic and environmental factors may affect the severity of sickling in an individual:

  • genetic factors
    • a higher than usual HbF level
    • coexisting thalassaemia
    • double heterozygosity (e.g. - HbSC)
    • other linked genetic polymorphism leading to severe or mild phenotypes
  • environmental factors - infection, climate, nutrition, psychosocial factors, socioeconomic status


Last reviewed 01/2018