The Southeast Asian 12.5 KB (delta-beta) degrees-deletion: a common beta-thalassemia in Mon-Khmer groups (Lao Theung) of South Laos

Abstract

Seven patients with unexplained anemia and mild thalassemic features were ascertained during a survey of hemoglobinopathies in the Sekong Province in South Laos. These patients belong to the Austroasiatic (Mon-Khmer) population of South Laos (official designation Lao Theung). Hemoglobin electrophoresis on cellulose acetate showed absence of Hb A and two bands in the positions of Hb E and Hb F respectively. Sequencing of DNA isolated from venous blood revealed the codon 26 G-->A mutation characteristic of the HBB*E gene, but none of the common Southeast Asian beta-thalassemia mutations were found. Detailed studies in four of the seven subjects identified a 12.5 kb deletion encompassing part of the delta-globin gene and the entire beta-globin gene. We conclude that this deletion is a common, and possibly the predominant beta-thalassemia mutation of the Austroasiatic Lao Theung population. Similar deletions reported in single individuals in Laos, Thailand and Vietnam are probably due to migrational spreading to areas adjacent to South Laos.