PCR-Based Detection of Southeast Asian (--Sea) and Filipino (--Fil) Alpha-Thalassemia Deletions in Filipino Patients
1,2Catherine Lynn Silao, 3Ernesto Yuson, 3Lisa Naranjo, 3Len Leporgo, 1,2Carmencita Padilla
1Institute of Human Genetics, National Institutes of Health Philippines, Manila, Philippines, 2Department of Pediatrics, University of the Philippines - Philippine General Hospital, Manila, Philippines, 3Fe del Mundo Children's Medical Center, Quezon City, Philippines
BACKGROUND: Alpha-thalassemia is the most common single-gene disorder in humans, stemming from mutations in the alpha-globin gene. The most common of these mutations are deletions which remove one or both of the two functional alpha-globin genes. Severity of disease characteristics depend on the number of deleted genes. Carriers of single- and double-gene deletions may either be asymptomatic or exhibiting mild microcytosis, with or without anemia, while those with three alpha-globin genes deleted suffer from Hb H disease which is characterized by a moderately severe hemolytic anemia with a variable clinical course. Deletion of all four alpha-globin genes lead to severe intrauterine anemia, resulting in fetal death. METHODOLOGY: To determine the molecular basis of alpha-thalassemia in Filipino patients, genomic DNA samples from 49 clinically diagnosed alpha-thalassemia patients were analyzed for the most common two-gene (cis) deletions found in Southeast Asian populations. Screening of these common deletions was done by polymerase chain reaction using primers flanking the deletion breakpoints of the Southeast Asian (--SEA) and Filipino (--FIL) deletions. RESULTS: Of the 49 samples analyzed, 10 were found positive for the Southeast Asian (--SEA) deletion while 9 were found to have the Filipino (--FIL) deletion. CONCLUSION: Our results reveal a prevalence pattern similar to other Southeast Asian populations, with the SEA deletion being the most prevalent and the Filipino deletion also showing a high incidence. Determination of the alpha-thalassemia mutations in Filipinos is useful in the genetic counseling and prenatal diagnosis of this disease.