Dominant beta-thalassaemia: a highly unstable haemoglobin is caused by a novel 6 bp deletion of the beta-globin gene

Beta-thalassaemia is inherited as an autosomal recessive trait in most families. Particular interest has recently been focused on the molecular pathology of the rare forms with a dominant mode of inheritance. The index patient and her mother, who are described in this report, displayed typical clinical and haematological features of beta-thalassaemia intermedia with significant ineffective erythropoiesis and additional peripheral haemolysis. Molecular analysis demonstrated a heterozygous genotype for a novel 6 bp (TGGTCT) deletion of the beta-globin gene involving codons 33-35. This deletion results in the removal of two valine residues from the beta-globin chain at position 33/34 (B15/B16) and the substitution of the tyrosine residue at position 35 (C1) by an aspartic acid (beta 33-35 [B15-C1] Val-Val-Tyr-->0-0-Asp). According to the index patient's place of birth, this abnormal haemoglobin has been termed Hb Dresden. The stability of the variant and the normal beta-globin chains were similar during the incubation period of in vitro globin chain synthesis analysis. However, Hb Dresden is exquisitely unstable and cannot be detected in the peripheral blood by haemoglobin electrophoresis, high-performance liquid chromatography (HPLC) or isoelectric focusing. This instability can be explained by the vital structural role of the three affected amino acids that, in normal haemoglobin, establish a total of nine intermolecular bonds (five hydrophobic and four polar) at both the alpha1beta1 (alpha2beta2) and the alpha1beta2 (alpha2beta1) interface.     

Common origin of a rare β‐globin initiation codon mutation (ATG→AGG) in Asians

In this report, we describe two Thai siblings presenting with mild hypochromic microcytic anaemia and splenomegaly since 2½ years of age. However, both patients were otherwise well with normal weight and height development and did not require transfusion during the 6‐year follow‐up period. Haematological and haemoglobin analyses were consistent with the clinical diagnosis of Hb E/β‐thalassaemia disease. To provide proper genetic counselling for this family, a definitive diagnosis of β‐thalassaemia was achieved using molecular analysis. We identified a rare initiation codon mutation (ATG→AGG) of the β‐globin gene in combination with the Hb E mutation (codon 26: GAG→AAG). The initiation codon mutation has previously been reported in several East Asian populations but has never been found in Southeast Asia and in combination with Hb E before. The haplotype analysis revealed a common origin of this mutation in the Asian population (5′: ? + ? + + ? +: 3′, type IV with framework 3 according to Orkin S, et al.). Although this rare mutation abolished the β‐globin expression and was considered as β⁰‐thalassaemia, the relatively mild phenotype in our patients may be attributed to a strong association between this mutation and the ?158 ^Gγ (C→T) polymorphism, an XmnI cleavage site (+), resulting in a high propensity of postnatal γ‐globin expression and ameliorating the clinical phenotypes.     

Flow cytometric determination of pre-transfusion red cell volume in fetuses and neonates requiring transfusion based on RhD+ dilution by transfused D- red cells

We report a case of feto-maternal haemorrhage and describe a new flow-cytometric method of determining a fetus's or infant's pre-transfusion red cell volume (RCV). We validate this method against an established technique, employing fetal haemoglobin (HbF) dilution, for determining the RCV in fetuses and neonates requiring intravascular transfusion. We discuss advantages and other potential applications of this new method.     

2型糖尿病患者糖化血红蛋白与超敏C反应蛋白的关系

目的探讨2型糖尿病患者糖化血红蛋白（HbA1c）与超敏C反应蛋白（hs-CRP）的关系。方法检测200例2型糖尿病患者的HbA1c、hs-CRP,同时选取100例健康体检者作为对照组。此外,根据200例2型糖尿病患者HbA1c四分位数水平进行临床分组,可分为A1组（HbA1c≤6.5%）、A2组（6.6%～7.9%）、A3组（8.0%～9.9%）、A4组（HbA1c≥10.0%）,同时将健康体检者列为A5组。分别统计对比各组患者hs-CRP水平。结果 2型糖尿病患者血清HbA1c、hs-CRP水平均明显高于健康体检者,差异均有统计学意义（P〈0.01）。五组hs-CRP水平比较差异有统计学意义（P〈0.01）,进一步两两比较发现,hs-CRP水平有随HbA1c增加而逐渐升高的趋势,A4组患者的血清hs-CRP水平显著高于其他四组（P〈0.01）。结论糖化血红蛋白与超敏C反应蛋白水平的显著升高是2型糖尿病患者普遍存在的一种现象,其中hs-CRP上升与HbA1c水平密切相关。     

Effect of Assorted Globin Haplotypes and α-Thalassemia on the Clinical Heterogeneity of Hb S-β-Thalassemia

Abstract

Hemoglobinopathies and thalassemias are the most commonly encountered monogenic disorders of blood in humans, posing a major genetic and public health problem round the globe. Hb S (HBB: c.20A>T)-β-thalassemia (β-thal) is a compound aberrant heterozygosity with inconsistent phenotypic expression, which are poorly described and clinically mapped. Comprehensive genetic characterization of such a population is highly warranted for complete understanding of the clinical heterogeneity, disease prognosis and therapeutic management. In this study, Hb S-β-thal (n?=?60) patients, strictly defined by varying degrees of clinical presentations, were selected to evaluate their genotype-phenotype agreement. Furthermore, β-globin (n?=?120) and α-globin gene clusters (n?=?60) were genetically characterized and statistically correlated with clinical terminologies to explain the clinical heterogeneity. Our results revealed the association of the Arab-Indian haplotypes with nine different frameworks of β-thal together with the modulating role of α-thalassemia (α-thal). The study subjects, including carriers of β-thal haplotype III [– – – – – – –] (8.0%), presented with varying severe patterns of clinical symptoms such as painful crisis, multiple infections and splenomegaly, as an outcome of significantly less Hb F and higher Hb S levels (p?<?0.5). The study findings indicated that together with α-thal, β-thal haplotypes and Hb F levels, may possibly provide a close justification to support the clinical heterogeneity in the study population.     

Hb Hubei [α114(GH2)Pro→His,HBA1: c.344C>A]: A Novel Hemoglobin Variant of the α1-Globin Chain

Abstract

We report here a novel α1-globin chain variant, Hb Hubei [α114(GH2)Pro→His, HBA1: c.344C>A], in a Chinese individual. The proband, a 28-year-old Chinese female, was discovered following routine Hb A_1c analysis using cation exchange high performance liquid chromatography (HPLC). Sanger sequencing revealed a novel missense mutation, HBA1: c.344C>A (CCC>CAC), in exon 2 of the α1-globin gene. The mutation caused a transition of proline to histidine at position α114(GH2) on the α1-globin chain. This new variant was named Hb Hubei after the geographic origin of the proband.     

A Novel β-Globin Gene Mutation: Hb Shenzhen [β90(F6)Glu→Ala,HBB: c.272A>C]

Abstract

We report a novel β-globin chain variant, Hb Shenzhen [β90(F6)Glu→Ala, HBB: c.272A>C], in a 52-year-old Chinese individual. The hemoglobin (Hb) variant takes the position of the Hb D zone using capillary electrophoresis. Sanger sequencing revealed a novel base mutation on the β-globin gene, HBB: c.272A>C, that resulted in a transition of glutamic acid to alanine at exon 2 of the β-globin gene. We named this novel variant Hb Shenzhen for the geographic origin of this proband.     

HB Kaohsiung or New York: A T→A Substitution at Codon 113 of the β-Globin Chain Creates an Alu i Cutting Site

Epidemiological studies and experimental data suggest iron involvement in atherosclerosis. The relation between iron and atherosclerosis is complex and remains contradictory. In thalassemia patients, non transferrin bound iron (NTBI) and free hemoglobin (Hb) are present in plasma and may accelerate atherogenesis, but its progression may be inhibited by iron chelators.

The mechanism whereby iron may stimulate atherogenesis has been intensively investigated. Non transferrin bound iron and sera from subjects with hemochromatosis induced endothelial activation with expression of vascular adhesion molecules and endothelial inflammatory chemokines. Such events could be inhibited by iron chelators and oxygen radical scavengers with intracellular activity. Iron chelators may be effective in preventing vascular damage in patients with high concentrations of NTBI as found in thalassemia.     

A Dutch Family with Hb Debrousse: Severe Anemia After Parvovirus B19 Infection

Hb Debrousse [β96(FG3)Leu→Pro] is an unstable hemoglobin (Hb) variant with high oxygen affinity. We describe a case of chronic compensated hemolysis in a 39-year-old woman in whom the variant was found. Soon after the diagnosis was made, she and her son were admitted to the hospital with severe anemia due to Parvovirus B19 infection. The son also appeared to have the Hb Debrousse variant. Parvovirus B19 infection is a life-threatening disease in patients with (compensated) hemolysis.     

β-THALASSEMIA INTERMEDIA FROM SOUTHERN IRAN: IVS-II-1 (G→A) IS THE PREVALENT THALASSEMIA INTERMEDIA ALLELE

The preliminary results of a pilot study are reported, intended as an initiation of a research plan, focused on the prevention of β-thalassemia in Iran. The aims of this study are: (i) to improve the knowledge of the molecular background of β-thalassemia intermedia in Southern Iran; (ii) to verify the role of the ?158 ^Gγ (C→T) (Xmn I) polymorphism as a modulating factor in thalassemia intermedia; (iii) to test the validity of the multiplex and single mutation specific amplification refractory mutation system in analyzing the molecular defects causing β-thalassemia in multiethnic populations; and (iv) to develop suitable strategies for the application of prevention protocols in Iran. To accomplish the task we have selected 87 β-thalassemia intermedia patients and adapted the DNA methodology to detect the following 11 frequent mutations in Iran: codon 5 (?CT); frameshift codons (FSC) 8/9 (+G); codon 30 (G→C); IVS-I-1 (G→A); IVS-I-5 (G→C); IVS-I-6 (T→C); IVS-I-110 (G→A); codons 36/37 (?T); codon 44 (?C); IVS-II-1 (G→A); IVS-II-745 (C→G). Because of the multiethnicity of the population we have also included the Indian IVS-I (25?bp deletion) and the Mediterranean IVS-I-130 (G→C) and codon 39 (C→T) mutations. Forty-eight patients were randomly studied for the Xmn I polymorphism together with 50 healthy volunteers as a control group. The molecular analysis conducted in Iran, identified only 31% of the alleles that were presumed to be thalassemic, revealing either a strategic or a technical insufficiency of the chosen method. However, the mutations with the highest prevalence in the country (IVS-II-1, IVS-I-110, IVS-I-1 and FSC 8/9) were found. As expected the IVS-II-1 defect, being the most frequent in south Iran, was present at the highest rate (24%). The Xmn I polymorphism was found in association with this prevalent mutation and was detected in the homozygous state in 87.5% of the patients homozygous for the IVS-II-1 (G→A) mutation. The overall positivity for Xmn I was found in 40.6% of the thalassemic alleles vs. 14% in the non-thalassemic, confirming the hypothesis of an older event, antecedent to the IVS-II-1 mutation. In trying to assess a more suitable molecular detection method we intend to continue this study in collaboration with the European centers involved, applying more effective technologies and better defining the molecular spectrum of β-thalassemia in the sub-populations. We also intend to verify the effect of α-thalassemia in the genotype/phenotype correlation of β-thalassemia intermedia.