Hematologic, Immunologic, and Neoplastic Disorders Practice Test 2026 - Free Questions and Study Guide

Alpha-thalassemia arises from deletions of alpha-globin genes on chromosome 16, and its frequency varies by historical malaria exposure. In populations where malaria was common, carriers gained some protection against severe malaria, so the allele persisted and became relatively common. This makes Southeast Asia and many parts of Africa regions with the highest prevalence. Regions with little historical malaria, like Northern Europe and Scandinavia, show much lower frequencies, and North America has variable frequencies due to diverse ancestry but generally not as high as malaria-endemic areas.