De novo initiation codon mutation (ATG→ACG) of the β-globin gene causing β-thalassemia in a swiss family

Investigation of microcytic anemia with normal ferrous status in two members (father and daughter) of a Swiss family originating from Bern revealed high levels of HbA₂ (4%, 7.3%) and HbF (3.2%, 3.1%). Direct sequence analysis of asymmetrically amplified DNA showed the ATGǎG mutation in the initiation codon of the β-globin gene. Heterozygous β-thalassemia was not found in either of the propositus's parents or in any of his brothers and sisters. Extended restriction fragment length polymorphism haplotyping of the β chromosomes led us to the conclusion of a recent spontaneous mutation in the paternal germ cell. The results of routine HLA and blood group testing supported the stated paternity. We also found that the intragenic sequence polymorphisms (frameworks) are not always in linkage disequilibrium with the Bam HI polymorphism downstream from the β-globin gene as previously observed. This is the second family found to carry this initiation codon mutation in the β-globin gene. Unlike the first reported family, of Yugoslavian origin, our patients have high HbF levels and this in the absence of a C→T substitution at-158 site 5′to Gγ. © 1993 Wiley-Liss, Inc.     

α‐thalassaemia masked by β gene defects and a new polyadenylation site mutation on the α2‐globin gene

We report three examples of chronic anaemia involving complex combinations of α‐ and β‐globin gene defects. The first case had a potential Hb H disease caused by the classic SEA/RW deletions masked by Hb E [β26(B8)Glu→Lys] in the homozygous state. The second had an unusual Hb H disease caused by compound heterozygosity for two different α2 polyadenylation site mutations masked by a β‐thalassaemia heterozygosity. The third had an intermediate α‐thalassaemia with considerable anaemia caused by an as yet unknown polyadenylation site (AATAAA>AATAAC) mutation in combination with a common RW deletion masked by a common Hb C [β6(A3)Glu→Lys] heterozygosity. Diagnostic methods, genotype/phenotype correlations and the chance of overlooking these combinations during risk assessment in a multiethnic society are discussed.     

Interaction of heterozygous βo-thalassemia with single functional α-globin gene

In this study, we analyzed the phenotypic manifestations resulting from the interaction of heterozygous β^o-thalassemia(β^o-39 nonsense mutation) with the functional loss of three α-globin structural genes in six subjects, of whom four had the [-αl–] α-globin genotype and two the [–/αThα] α-globin genotype. The β-thalassemia defect was in all cases the nonsense mutation at codon 39. The nondeletion α-thalassemia α^th was the initiation codon mutation (AUG→GUG) of the α-2 gene. In all these subjects hypochromia and microcytosis were more marked than in βα -thalassemia heterozygotes with a full complement of four α-globin genes. All but one had moderate anemia. The α:β globin chain synthesis ratios were consistently decreased. No cases had Hb H on electrophoresis. Subjects with [–/αThα] α-globin genotype had more severe thalassemia-like manifestations than those with [–/-α] α-globin genotype.     

Haematological phenotypes in a family with triplicated α-globin gene, β∘39 and δ+27 thalassaemia mutations

Summary In this paper we report an unusual Sardinian family, in which the heterozygosity for β°₃₉-thalassaemia and for triple α-globin gene complex have been found in two members: the former showing a high HbA₂ mild thalassaemia intermedia syndrome, the latter, her daughter, showing a normal HbA₂ thalassaemia trait. Molecular analysis revealed the daughter to also be a carrier of a δ⁺_27-thalassaemia point mutation, which in trans to the β°₃₉ defect invariably normalizes the HbA₂ levels.     

Haplotypes of the human β-like globin gene cluster: Analyzing the 3′ Hpa I polymorphic site by long distance PCR

Haplotypes of the β-like globin gene cluster in individuals with sickle cell disease appear to be important as prognostic factors for the severity of the disease. The Hpa I polymorphic site 3′ of the β-globin gene is very often involved in haplotyping. However, this restriction site cannot be ascertained by conventional PCR, as it is in the middle of a long repetitive sequence. Long distance PCR was employed to amplify this Hpa I-containing region. By positioning either one or both primers outside the repetitive sequence, specific amplification was achieved. Moreover, sufficient amplification can be obtained by using a white cell lysate instead of purified DNA, thereby significantly reducing the amount of blood needed, and the total procedure time.     

Deep vein thrombosis followed by internal jugular vein thrombosis as a complication of in vitro fertilization in a woman heterozygous for the prothrombin 3' UTR and factor V Leiden mutations

Thrombosis of the internal jugular vein is a rare event but one that can have serious consequences. Most cases reported in the literature have occurred in patients with indwelling central venous catheters, in association with head and neck sepsis, or in hypercoagulable states. However, a small number of cases have been associated with in vitro fertilization and more often with the ovarian hyperstimulation syndrome (OHSS). We report the case of a 30-year-old woman heterozygous for both the prothrombin 3' UTR mutation and for the factor V Leiden mutation who presented with a proximal deep vein thrombosis following in vitro fertilization. She subsequently developed an internal jugular vein thrombosis extending into the subclavian and axillary vein despite therapeutic anticoagulation with a low molecular weight heparin. Thromboembolic events can occur in the absence of other clinical features of OHSS, especially in patients with underlying prothrombotic abnormalities. Neck pain and swelling in a pregnant woman, especially one that has undergone in vitro fertilization, should be taken seriously and investigated with duplex scanning and/or MRI. Women with a personal or family history of thrombosis undergoing in vitro fertilization should be made fully aware of the potential thrombotic risks and should be considered for a thrombophilia screen.     

Detection of the (–SEA) double α-globin gene deletion by a simple immunologic assay for embryonic ζ-globin chains

Homozygous α-thalassemia [α-thal-1], with loss of all four α-globin genes, causes lethal hydrops fetalis. The most common mutation producing this syndrome is the Southeast Asian (–^SEA ) double α-globin gene deletion. Erythrocytes from adults heterozygous for the (–^SEA ) deletion have minute amounts of embryonic ζ-globin chains detectable by anti-ζ-globin monoclonal antibodies. Among 225 peripheral blood samples tested by a simple anti-ζ-immunobinding tetra-zolium dye test, 81 were positive and 144 were negative. The majority of subjects were of Filipino, Chinese, or Laotian ancestry. All 81 positive samples were confirmed by Bam HI digests and a ζ-cDNA probe to have the (–^SEA ) mutation. The (–^SEA ) double α-deletion was the only abnormality in 58. In the others, it was combined with α-globin or β-globin mutations, or coincidental iron deficiency. Four other samples from (–^SEA ) heterozygotes were negative by this immunologic assay. Anti-ζ negative samples included 78 deletions of the total α-globin region, (–^Tot), 23 single α-globin deletions, and a variety of β-globin mutations; 16 normocytic samples with normal α-genes were also negative. Ten anti-ζ positive and 25 anti-ζ negative samples had benign triplicated ζ-globin genes. In this population, the sensitivity of this test was 95%; and specificity for the (–^SEA ) mutation was 100%. Anti-ζ immunobinding testing provides rapid, simple, and reliable screening for the (–^SEA ) double α-globin deletion, although it does not detect the (–^Tot) total α-deletions. © 1993 Wiley-Liss, Inc.