Because thalassemia heterozygosity confers some
immunity against malaria, there is a particularly high incidence of
thalassemia (2.5%-25%) in the Mediterranean basin, the Middle
East, the tropical and subtropical regions of Africa, the Asian
subcontinent, and Southeast Asia, where milder forms of the
disease are most commonly seen. Cases of thalassemia also occur
sporadically in virtually every ethnic group and geographic
location.2,3