PREVALENCE OF ALPHA-THALASSEMIAS IN NORTHERN THAILAND

The population of northern Thailand has one of the highest frequencies of alpha-thalassemia in the world. However, the available distributio nal data are controversial. In addition to deletional types of alpha-t halassemia Hb, type Constant Spring should also be taken into consider ation in alpha-thalassemia population studies, because it causes clini cal alpha-thalassemia in the homozygous state or when present with bot h alpha-globin genes deleted in trans. We have examined a sample of 21 5 healthy subjects from four rural districts of Chiang Mai province. O ut of these, 77 exhibited anomalies of the alpha-globin genes (alpha a lpha/-alpha(3.7) in 36; -alpha(3.7)/-alpha(3.7) in 3; --(SEA) in 30; a lpha alpha/alpha(CS)alpha in 5; alpha alpha alpha(anti3.7) in 3). Ther efore, no fewer than 2% of the children in northern Thailand are expec ted to be born with HbH disease or thalassemic hydrops fetalis. The co nsiderable public health problem of hemoglobinopaties and the increasi ng acceptance of family planning necessitates facilities for the pre-a nd postnatal diagnosis of these disorders at the DNA level.