What ethnicity is commonly affected by sickle cell disease?

Ethnicity Most Commonly Affected by Sickle Cell Disease

Sickle cell disease most commonly affects people of African or African-Caribbean descent, with 98% of patients registered in the UK National Haemoglobinopathy Registry being of African or Caribbean background. 1

Epidemiology and Global Distribution

Sickle cell disease (SCD) is one of the most common serious inherited single gene disorders worldwide. The distribution varies significantly by geographic region and ethnic background:

• African/African-Caribbean: The vast majority of SCD cases occur in people with African ancestry. In the UK, 98% of registered patients are of African or Caribbean background 1
• Mediterranean: SCD is also seen in families originating from Mediterranean countries 1
• Middle Eastern: Individuals from the Middle East have higher prevalence than the general population 1
• Indian subcontinent: SCD is present in families from India and the southern/eastern Mediterranean 1

Geographic Distribution in the UK

• Approximately two-thirds of patients with SCD in the UK live in London
• The remaining one-third live in cities in the North West, West Midlands, East Midlands, or Yorkshire and Humber 1

Genetic and Evolutionary Context

The high prevalence of sickle cell trait in certain populations is linked to evolutionary pressure from malaria:

• The HbS mutation in the β-globin gene provides protection against malarial infection in heterozygous carriers (sickle cell trait) 1
• This evolutionary advantage has maintained the mutation at high frequencies in malaria-endemic regions, particularly in sub-Saharan Africa 1
• Similar selective pressure has influenced other genetic adaptations to malaria in African, Mediterranean and Asian populations, such as G6PD variations 1

Global Burden

• An estimated 300,000-400,000 infants are born with SCD globally each year 2, 3
• The majority of these births occur in sub-Saharan Africa 2, 3
• In the US, approximately 100,000 people live with SCD 2
• In the UK, there are approximately 14,000 patients with SCD 1

Clinical Implications of Ethnicity

Understanding the ethnic distribution of SCD is important for:

1. Screening programs: Many countries have implemented universal newborn screening, but this remains challenging in low-income, high-burden settings 3
2. Genetic counseling: Particularly important for individuals from high-risk ethnic backgrounds
3. Healthcare resource allocation: In areas with significant populations of affected ethnic groups

Common Pitfalls and Caveats

• Assuming SCD only affects Black populations: While most common in those of African descent, SCD also affects people from Mediterranean, Middle Eastern, and South Asian backgrounds
• Overlooking mixed ancestry: With increasing multiethnic partnerships, there are changing patterns in SCD distribution, including increased numbers of variant forms like Hb SE disease 4
• Confusing trait with disease: Sickle cell trait (carrier status) is much more common than sickle cell disease and is present in approximately 240,000 healthy carriers in the UK 1
• Failing to screen appropriately: Universal screening of newborns from at-risk ethnic backgrounds is recommended to enable early diagnosis and preventive care 5

Understanding the ethnic distribution of SCD is crucial for appropriate screening, early diagnosis, and optimal management to reduce morbidity and mortality in affected populations.