IthaID: 1504

Also known as: HPFH-6

Comments: The deletion is reported in members of Thai families. In one family, the propositus was diagnosed as heterozygous for δβ-thalassaemia and β-thalassaemia, presenting with a thalassaemia intermedia clinical phenotype. Analysis of HbF showed only Gγ chain with pancellular but uneven distribution in erythrocytes. Following restriction mapping, the 5’end of the deletion appeared to reside near the EcoRI site 3’ to the Gγ gene [PMID: 2889616]. In another family, the propositus and two siblings were diagnosed as compound heterozygous for δβ-thalassaemia and β-thalassaemia, presenting clinically as thalassaemia intermedia. The father and two other siblings were carriers for this deletion and had raised % HbF (mainly Gγ chains) with pancellular distribution in their erythrocytes. Gene mapping showed that the deletion starts at the HindIII site 3' to the Gγ gene, and extends to a region more than 45 kb from the 3' end of the β gene. The deletion was reported to span more than 70 kb [PMID: 2272841]. In a subsequent study, sequence analysis showed that the 5' breakpoint of this deletion was located 1159 bp downstream of the third exon of the Gγ gene. The 3' breakpoint was located 524 bp upstream of an enhancer element (LOC110013311), lying approximately 52.7 kb downstream of the β gene [PMID: 9272169]. The enhancer element is removed in the Chinese (Aγβδ)0-thal deletion [IthaID: 1527].

We follow the HGVS sequence variant nomenclature and IUPAC standards.

Heterozygous records (preview in IthaPhen)

1. Fucharoen S, Winichagoon P, Chaicharoen S, Wasi P, Different molecular defects of G gamma (A gamma delta beta)o-thalassaemia in Thailand., Eur. J. Haematol., 39(2), 154-60, 1987 PubMed
2. Winichagoon P, Fucharoen S, Thonglairoam V, Wasi P, Thai G gamma (A gamma delta beta)zero-thalassemia and its interaction with a single gamma-globin gene on a chromosome carrying beta zero-thalassemia., Hemoglobin, 14(2), 185-97, 1990 PubMed
3. Kosteas T, Palena A, Anagnou NP, Molecular cloning of the breakpoints of the hereditary persistence of fetal hemoglobin type-6 (HPFH-6) deletion and sequence analysis of the novel juxtaposed region from the 3' end of the beta-globin gene cluster., Human genetics, 100(3), 441-5, 1997 PubMed