What ethnic groups are most commonly affected by thalassemia?

Ethnic Groups Most Commonly Affected by Thalassemia

Thalassemia predominantly affects individuals originating from the Mediterranean region, Middle East, Transcaucasia, Central Asia, Indian subcontinent, and Southeast Asia, with alpha thalassemia being particularly common among Southeast Asian populations. 1, 2

Geographic Distribution of Thalassemia

Alpha Thalassemia

• Southeast Asian populations: Alpha thalassemia is most common in this region, where it accounts for 28-55% of nonimmune hydrops fetalis cases 3
• The severe form of alpha thalassemia typically leads to hydrops fetalis and fetal demise if not diagnosed and treated early 3

Beta Thalassemia

• Mediterranean populations (Italy, Greece, Cyprus)
• Middle Eastern populations
• Transcaucasian and Central Asian populations
• Indian subcontinent
• Southeast Asian populations
• Limited incidence in African populations 4

Prevalence Patterns and Migration Impact

• Thalassemia is common in regions with historically prevalent malaria, as thalassemic red cells provide immunity against the malaria parasite 2
• Migration from thalassemia-prevalent countries to non-prevalent regions (primarily North America and Central/North Europe) has changed the global distribution pattern 2
• This migration creates challenges in healthcare systems not traditionally equipped with established prenatal screening programs for thalassemia 2

Genetic Variations by Region

• Despite the heterogeneity of thalassemia (with more than 150 different molecular defects identified), each at-risk population has its own spectrum of common mutations (usually 5-10) 4
• Chinese populations in different regions share similar mutation patterns, but these differ significantly from other ethnic groups in Southeast Asia 5
• Similar β-thalassemia mutation spectrums have been found among Thai, Malaysian Chinese, and Guangdong (Southern China) populations 5

Screening Recommendations

• The American College of Medical Genetics recommends targeted screening for individuals with ancestry from:

  • Mediterranean regions
  • Middle East
  • Africa
  • Southeast Asia 1

• For screening in these high-risk populations:

  1. Complete blood count (CBC) with red blood cell indices as initial screening
  2. Hemoglobin electrophoresis or high-performance liquid chromatography (HPLC) if microcytosis with normal or elevated RBC count is found 1

• In pregnant women from these ethnic backgrounds, mild anemia unresponsive to iron therapy may indicate thalassemia minor or sickle cell trait 3

Clinical Implications

• Parents can be screened by evaluation of mean cell volume (MCV), which will be <80 fL in thalassemia carriers 3
• Genetic counseling is essential for families with thalassemia history, particularly those from high-risk ethnic groups 1
• Comprehensive prevention programs involving carrier detection, molecular diagnostics, genetic counseling, and prenatal diagnosis have been successful in many countries in Europe, Asia, and Australia 6

Historical Perspective

While thalassemia is historically considered an Old World disease, archaeological evidence has found potential cases in prehistoric Native American populations, suggesting the condition may have existed more broadly than previously thought 7. However, the prevalence remains significantly higher in the traditional high-risk regions identified above.