IthaID: 1505

Also known as: Vietnamese, SE Asian, HPFH-7, SEA-HPFH, 27 kb deletion

Comments: The deletion comprises the entire β-globin gene with a total deletion length of 27 kb, resulting of a non-homologous recombination event. In the first time reported as Vietnamese HPFH deletion with approximate size of 30 kb [PMID 7689901]. The 5′ breakpoint is located ~3.5 kb downstream of the δ-globin gene, while the 3' breakpoint is located ~2.3 kb downstream from the 3′ HS-1 site (γ-silencing element) of the β-globin gene. Recent studies determined the exact breakpoints of the deletion and patients haematological indices (microcytosis and increased Hb A2) indicated that the SEA deletion is more akin to a β-thal phenotype with raised HbF, because of the deletion of γ-silencing element.

We follow the HGVS sequence variant nomenclature and IUPAC standards.

Heterozygous records (preview in IthaPhen)

1. Motum PI, Hamilton TJ, Lindeman R, Le H, Trent RJ, Molecular characterisation of Vietnamese HPFH., Human mutation, 2(3), 179-84, 1993 PubMed
2. Dimovski AJ, Divoky V, Adekile AD, Baysal E, Wilson JB, Prior JF, Raven JL, Huisman TH, A novel deletion of approximately 27 kb including the beta-globin gene and the locus control region 3'HS-1 regulatory sequence: beta zero-thalassemia or hereditary persistence of fetal hemoglobin?, Blood, 83(3), 822-7, 1994 PubMed
3. Xu XM, Li ZQ, Liu ZY, Zhong XL, Zhao YZ, Mo QH, Molecular characterization and PCR detection of a deletional HPFH: application to rapid prenatal diagnosis for compound heterozygotes of this defect with beta-thalassemia in a Chinese family., Am. J. Hematol., 65(3), 183-8, 2000 PubMed
4. So CC, So AC, Chan AY, Tsang ST, Ma ES, Chan LC, Detection and characterisation of beta-globin gene cluster deletions in Chinese using multiplex ligation-dependent probe amplification., J Clin Pathol, 62(12), 1107-11, 2009 PubMed
5. Cai WJ, Li J, Xie XM, Li DZ, Screening for common β-globin gene cluster deletions in Chinese individuals with increased hemoglobin F., Int J Lab Hematol, 37(6), 752-7, 2015 PubMed
6. He S, Wei Y, Lin L, Chen Q, Yi S, Zuo Y, Wei H, Zheng C, Chen B, Qiu X, The prevalence and molecular characterization of (δβ)(0) -thalassemia and hereditary persistence of fetal hemoglobin in the Chinese Zhuang population., J. Clin. Lab. Anal. , 2017 PubMed