Distribution of thalassemias and associated hemoglobinopathies identified by prenatal diagnosis in Taiwan.

BACKGROUND: Hemoglobin (Hb) gene disorders are common hereditary disorders in Taiwan, and α- and ß-thalassemias are among the well-known Hb disorders here. Our study provides a primary reference for designing a locally relevant antenatal diagnostic test to control the spread of thalassemia. METHODS: Between 1998 and 2011, prenatal diagnoses for identifying thalassemia and hemoglobinopathies were performed on 1240 fetuses at risk for α-hydrops and ß-thalassemia major. RESULTS: Of 1240 specimens analyzed, 1082 (87%) were obtained by amniocentesis; 125 (10%), by chorionic villus sampling; and 33 (3%), by cordocentesis. Prenatal diagnoses revealed that 21.5% of these fetuses as thalassemia major (including α-thalassemia hydrops, ß-thalassemia major, and Hb E/ß-thalassemia); 50.2%, for thalassemia minor (include α-thalassemia carrier, ß-thalassemia carrier, and α-thalassemia combined ß-thalassemia carrier); and 28.3% for normal type (include non-α, ß-thalassemia). The most common α-hydrops were SEA (Southeast Asian) and Philippine type (frequencies of 74.91 and 5.24%, respectively). The frequency of the IVS-II-654 combined codons 41/42 mutation, the most common ß-thalassemia major mutation in this region, was 5.24%. Two fetuses were found with E/ß-thalassemia (HbE/IVS-II-654 and HbE/codons 41/42, respectively). Since 1993, Taiwan's Department of Health adopted a national program for screening pregnancies to control spread of thalassemia. In the last 10years, less than 3 such cases have occurred per year. After 2003, this number was 0 for a total of 4years (2003, 2004, 2007, and 2008). CONCLUSION: In Taiwan, incidence and frequency of thalassemia genotypes were similar to those previously reported. The national program for screening pregnancies to control spread of thalassemia that resulted in a marked decline in the number of newborns with thalassemia major. Interestingly, prenatal diagnoses revealed 21.5% for thalassemia major, 50.2% for thalassemia minor, 28.3% normal comparison of thalassemia type distribution showed normal type increasing by 13.2% and major type decreasing by 14%. This unique and significant finding needs further clinical studies and discussion to explain such a phenomenon.

Molecular lesion frequency of hemoglobin gene disorders in Taiwan.

Hemoglobin (Hb) gene disorders are common inherited diseases in Taiwan. The α- and ß-thalassemias are among the well-known Hb diseases in this area. We reviewed abnormal hematological data in 3578 cases, identified between 1998 and 2009, as being at-risk for α-thalassemia (α-thal) (n = 1909; 53.3%), ß-thal (n = 743; 20.8%), non-α, ß-thal (n = 872; 24.4%), and α-thal combined with ß-thal (n = 54; 1.5%), and collected fetal blood samples for prenatal testing. The most common types of α(0)- and α(+)-thal were the SEA (Southeast Asian) deletion and the -α(3.7) rightward deletion, with frequencies of 87.79 and 4.85%, respectively. The frequency of the IVS-II-654 (C>T) mutation, the most common ß-thal mutation in this region, was 38.6%. Hb E [ß26(B8)Glu→Lys, GAG>AAG] was found to be the most common Hb variant, and it was concluded that Hb Tak [ß147 (+AC)], Hb G -Taichung (also known as Hb Q-Thailand) [α74(EF3)Asp→His, GAC>CAC (α1)], Hb Owari [α121(H4)Val→Met (GTG>ATG)], and Hb Phnom Penh [α117(GH5)Phe-Ile-α118(H1)Thr (α1)] were very rare. The results of this study provide a primary reference for designing a locally relevant antenatal diagnostic test for controlling the spread of thalassemia.