Prevalence and molecular characterization of beta-thalassemia in Filipinos

Beta-thalassemia (thal) is a common single-gene disease worldwide. However, the prevalence of beta-thal and the spectrum of beta-globin gene mutations in Filipinos remain unclear. This study sought to answer these two questions. A total of 2954 apparently healthy Filipinos in Taiwan were recruited for a prevalence study. A complete blood count was done in every subject. Those with microcytosis were studied with hemoglobin (Hb) high-performance liquid chromatography to determine the levels of Hb A2 and Hb F. Twenty-seven subjects had elevated levels of Hb A2 (>4.0%). These 27 suspected beta-thal carriers and another 16 beta-thal major patients who were being treated in the Philippines were studied to determine the spectrum of beta-globin gene mutations. Gap-PCR was used to detect the Filipino deletion of beta-thal, and direct sequencing was used to detect point or small mutations in the beta-globin gene. All of the 27 suspected beta-thal carriers had one mutation in the beta-globin gene, resulting in an overall prevalence of 0.9%. The spectrum of beta-thal mutations was similar in the carrier and patient groups. Analysis of the pooled identified seven different mutations in the study population. The Filipino deletion was the most common mutation, accounting for 45.8% (27/59) of the alleles, followed by codon 67 (-TG) (16 alleles), and Hb E (11 alleles). These three mutations accounted for 92% of the Filipino beta-thal alleles. Elucidation of the beta-thal mutations in Filipinos is useful for the genetic counseling and prenatal diagnosis of this disease.