Compound Heterozygosity for Hb Alperton (HBB: c.407C>T) and IVS-I-5 (G>C) (HBB: c.92+5G>C) Mutations Presenting as a Moderate Anemia in an Indian Family

While knowledge of HBB gene mutations is necessary for offering prenatal diagnosis (PND) of β-thalassemia (β-thal), a genotype-phenotype correlation may not always be available for rare variants. We present for the first time, genotype-phenotype correlation for a compound heterozygous status with IVS-I-5 (G>C) (HBB: c.92+5G>C) and HBB: c.407C>T (Hb Alperton) mutations on the HBB gene in an Indian family. Hb Alperton is a very rare hemoglobin (Hb) variant with scant published information about its clinical presentation, especially when accompanied with another HBB gene mutation. Here we provide biochemical as well as clinical details of this variant.     

Rare Hemoglobin Variants: Hb G-Szuhu (HBB: c.243C>G), Hb G-Coushatta (HBB: c.68A>C) and Hb Mizuho (HBB: c.206T>C) in Sri Lankan Families

Abstract

In this short communication, we describe the clinical presentation of unusual hemoglobin (Hb), variants in three Sri Lankan cases under study for β-thalassemia intermedia (β-TI). We believe this is the first report on their occurrence in Sri Lanka as well as from the Indian subcontinent. During a molecular study performed on β-TI patients, we identified three unusual Hb variants as Hb G-Szuhu (HBB: c.243C>G), Hb G-Coushatta (HBB: c.68A>C) and Hb Mizuho (HBB: c.206T>C) in three unrelated families. Hb G-Szuhu and Hb G-Coushatta were found in combination with the common β-thalassemia (β-thal) mutation, IVS-I-5 (G>C). Both probands had mild anemia with greatly reduced red cell indices and had non palpable livers and spleens, however, by ultrasound, both were observed to be enlarged. The final Hb variant, Hb Mizuho, was identified as a heterozygous mutation found in both proband and his mother. Both family members had severe anemia and were regularly transfused and had increased red cell parameters.     

β-Thalassemia Major Resulting from Compound Heterozygosity for HBB: c.92+2T>C [formerly known as IVS-I-2 (T>C)] and a Novel β0-Thalassemia Frameshift Mutation: HBB: c.209delG; p.Gly70Valfs*20

A novel β⁰-thalassemia (β-thal) frameshift mutation, HBB: c.209delG; p.Gly70Valfs*20, is described in a 21-year-old African American female with β-thalassemia major (β-TM) due to compound heterozygosity for the β⁰-thal mutation HBB: c.92+2T>C [formerly known as IVS-I-2 (T>C)] and HBB: c.209delG. The combination of these mutations demonstrates a complete lack of β-globin chain synthesis, evidenced by the proband having no Hb A present.     

Hb Hornchurch [β43(CD2)Glu→Lys; HBB: c.130G>A] Compromises the Molecular Diagnosis of β-Thalassemia in a Chinese Family

The combination of β-thalassemia (β-thal) and a hemoglobin (Hb) variant is not uncommon in regions with a high prevalence of thalassemia. Although most of the β-globin chain variants will not aggravate the β-thal, some can compromise the accurate molecular diagnosis. In this study, we present a rare case of coinheritance of β-thal and Hb Hornchurch [β43(CD2)Glu→Lys; HBB: c.130G>A], that compromises the molecular diagnosis of homozygous β-thal.     

First Report on the Coinheritance of α-Thalassemia and a Rare β-Thalassemia Compound Heterozygosity for the IVS-I-I(G>A)/IVS-II-705(T>G) Mutations in a Syrian Family

We describe a proband originating from Al-Quneitra Province, Syria. His hematology data was as follows: Hb A 24.7%, Hb F 71.1%, Hb A₂ 4.2%. Molecular analysis, based on DNA sequencing of the β-globin gene mutation, showed for the first time a compound heterozygous IVS-I-1 (G>A) (HBB: c.92+1G>A)/IVS-II-705 (T>G) (HBB: c.316-146T>G) on the β-globin gene. A reverse hybridization technique revealed that the proband was also an α-thalassemia (α-thal) –α^3.7 (rightward) deletion carrier. Haplotypes analysis for the seven polymorphic restriction sites showed that the compound heterozygous mutations, IVS-I-1/IVS-II-705, were linked to two haplotypes: I [+ – – – – + +] and VI [– + + – – – +], respectively. Our results showed, for the first time, the presence of rare β-thalassemia (β-thal) IVS-II-705 (T>G) mutation associated with IVS-I-1 (G>A). Our findings suggest the presence of these mutations resulted from past migrations.     

Rare Association of Hb D-Los Angeles (HBB: c.364G>C) with Hb H Disease: Diagnosis and Clinical Implications

Abstract

Hb D-Los Angeles (or Hb D-Punjab) (HBB: c.364G?>?C) is found worldwide and is derived from a point mutation in the β-globin gene prevalent in the Punjab region of Northwestern India. Heterozygous or homozygous inheritance does not cause significant medical problems, whereas association with other hemoglobinopathies, especially β-thalassemia (β-thal) and sickle cell disease, changes the phenotype. Coinheritance of Hb D-Los Angeles with Hb H disease (α–/–?–) has never been reported before. The presence of this rare combination in a family of Greek origin is herein described, and the challenges involving clinical management are discussed.     

Hb Grand Junction (HBB: c.348_349delinsG; p.His117IlefsX42): A New Hyperunstable Hemoglobin Variant

Hyperunstable hemoglobinopathy (HUH) [dominantly inherited β-thalassemia (β-thal)] is a relatively rare form of congenital hemolytic anemia in which mutations occur in the genes encoding for α and β chains, or both chains of the hemoglobin (Hb) molecule. We describe two Hispanic adolescents with a new unstable Hb variant (HBB: c.348_349delinsG; p.His117IlefsX42), resulting from a frameshift mutation at codons 115/116 of the β-globin gene. Both patients also have a 3.7?kb deletion on one α gene, leading to a decreased imbalance between α and β chain formation, and subsequently a milder phenotype than that seen in other hyperunstable Hb variants.     

The Clinical and Laboratory Spectrum of Hb C [β6(A3)Glu→Lys,GAG>AAG] Disease

Newborn screening (NBS) provides early diagnosis of sickle hemoglobinopathies. After Hb S [β6(A3)Glu→Val, GAG>GTG], Hb C [β6(A3)Glu→Lys, GAG>AAG] is the most common hemoglobin (Hb) abnormality identified in the United States (1,2). Published data regarding children with Hb C disease are limited. This study was conducted to summarize a single institution’s clinical and laboratory data for patients with Hb C disease, specifically homozygous Hb CC and its variants over a 10-year period. Forty-seven patients, whose mean age at diagnosis was 2.9 years (range 0.04 to 23 years), were identified. Twenty-nine had Hb CC and the remainder had compound heterozygous variants [10 Hb C/β⁺-thalassemia (β⁺-thal), four Hb C/β⁰-thal, and one each with Hb C/Hb Hope or β136(H14)Gly→Asp (GGT>GAT), Hb C/Hb Lepore (a hybrid δβ-globin gene), Hb C/HPFH (hereditary persistence of fetal Hb) [probably a ^Gγ HPFH-2 (the Ghanaian type)], and Hb C/Osu-Christiansborg or β52(D3)Asp→Asn (GAT>AAT)]. All patients had mild microcytic anemia with reticulocytosis and frequent target cells on peripheral smear. Splenomegaly or cholelithiasis occurred in 2.6% of patients <8 years of age, however, these symptoms were more common (71.0%) in patients >8 years of age. No patient had serious infections or painful events resembling vasoocclusion. Accurate diagnosis and understanding of Hb C-related disorders helped to avoid confusion with sickle hemoglobinopathies and aided in proper clinical management.     

A Clinical Update of the Hb Siirt [β27(B9)Ala→Gly; HBB: c.83C>G] Hemoglobin Variant

We report a clinical update of the hemoglobin (Hb) variant [β27(B9)Ala→Gly; HBB: c.83C>G], named Hb Siirt, that was previously described as a silent variant in a 23-year-old Kurdish female. The patient was also a carrier of the codon 5 (–CT) (HBB: c.17_18delCT) frameshift mutation and of the ααα ^{anti 3.7} triplication. Her initial moderate β-thalassemia intermedia (β-TI) phenotype worsened with time, causing the patient to become a transfusion-dependent subject at the age of ～40 years. Subsequent molecular characterization of both parents revealed that the Hb Siirt variant was inherited by the mother, while the other two globin alterations (HBB: c.17_18delCT and ααα^{anti 3.7} triplication) were genetically transmitted by the father. The latter remained a carrier of a mild β-TI phenotype throughout his life, at least until the age of 65 years. We hypothesize that the worsened clinical conditions in the daughter were due to the additional, maternally inherited Hb Siirt variant. However, protein 3D conformational analysis did not seem to reveal substantial overall structural changes. Among the other three described variants [Hb Volga (HBB: c.83C>A), Hb Knossos (HBB: c.82?G>T), Hb Grange-Blanche (HBB: c.83C>T] that are due to nucleotide substitutions at codon 27 of the β-globin gene; only Hb Knossos causes a β⁺-thalassemia (β⁺-thal) phenotype.     

A Novel Pathogenic β-Thalassemia Mutation Identified at Codon 8 (HBB: c.27delG) in a Bangladeshi Family Acquired De Novo

Abstract

In Bangladesh, the practice of β-thalassemia (β-thal) carrier screening and prenatal diagnosis (PND) by β-globin gene sequencing has been initiated to prevent the birth of affected children. The study aimed to describe a novel de novo mutation of the β-globin gene and its clinical implication. Out of 100 Bangladeshi β-thal carrier families, one patient with hematological and clinical features associated with β-thal and her parents were included. Molecular characterizations of β-globin gene mutations were performed by direct sequencing. A novel nucleotide deletion mutation at codon 8 in the first exon of the β-globin gene (HBB: c.27delG) was found in a 1-year-old child of the studied family in a heterozygous state along with common Hb E (HBB: c.79G>A). The mutation caused a frameshift to a new stop codon at codon 18 resulting in a β⁰-thal phenotype. The proband exhibited a β-thal intermedia (β-TI)-like genotype, however, showed β-thal major (β-TM)-like complications and was transfusion-dependent. Her mother had a profile consistent with the Hb E trait, while the father had normal hematological indices. Mutation analyses revealed the mother to be heterozygous for Hb E, while the father had a normal genotype. The novel mutation was assumed to be inherited de novo by the paternity test. The study documented a novel pathogenic mutation in the β-globin gene in a Bangladeshi family by β-globin gene sequencing.     

Regulatory Single Nucleotide Polymorphism rs368698783 (G>A): a Genetic Modifier of Hb F Production Only under Erythropoietic Stress Characteristic for β-Globin Chain Deficiency?

A regulatory single nucleotide polymorphism (rSNP), the ^Aγ (+25?G>A) (rs368698783) (NG_000007.3: g47783G>A) located in the HBG1 proximal promoter, is a significant predictor of clinical severity by elevating Hb F levels in β-thalassemia (β-thal). In this study, the presence of the ^Aγ (+25?G>A) and ^Aγ (+25?A>A) genotypes was investigated in four subgroups from a total of 611 subjects, including 88 α-thalassemia (α-thal) carriers (group A), 162 β-thal carriers of point mutations (group B), 57 carriers of β-thal deletions (group C) and 152 non thalassemic individuals (group D). The result is that the genotypes G>A and A>A exhibit significantly high levels of Hb F compared with the genotype G>G in both groups B and C, while no significant difference was observed in both groups A and D. We assume that the effect of ^Aγ (+25?G>A) polymorphism on Hb F production is only under erythropoietic stress characteristic for β-globin chain deficiency.     

A Novel β-Thalassemia Insertion/Frameshift Mutation Between Codons 77/78 (p.Leu78Profs*13 or HBB: c.235_236insC) Observed in a Family in Bangladesh

β-Thalassemia (β-thal) is one of the most common inherited hemoglobin (Hb) disorders, worldwide. A 28-year-old female and her husband came to Dhaka Shishu (Children) Hospital, Bangladesh for prenatal diagnosis for thalassemia mutations. We identified and characterized a novel β-thalassemia (β-thal) mutation due to an insertion of cytosine between codons 77 and 78 (p.Leu78Profs*13) found in mother in a heterozygous state. This mutation caused an insertion in the normal reading frame of the β-globin coding sequence and the new stop codon being the amino acid 90 (HBB: c.235_236insC) in exon 2 that leads to a β⁰-thal phenotype.     

High Hb A2 β-Thalassemia Due to a 468 bp Deletion in a Patient with Hb S/β-Thalassemia

We describe a case of Hb S/β-thalassemia (thal) involving a 468 bp deletion that removes the β-globin gene promoter but leaves the coding regions intact. This is the second report of this deletion, and our family study establishes that this deletion causes β⁰-thal with unusually high levels of Hb A₂ and Hb F. As with other genotypes involving deletions of the 5′ region of the β-globin gene, our patient had a mild form of Hb S/β-thal.     

THE Hb S/β+-Thalassemia Phenotype Demonstrates that the IVS-I (−2) (A>C) Mutation is a Mild β-Thalassemia Allele

We report a family in which two siblings are compound heterozygotes for Hb S [β6(A3)Glu→Val] and a rare β-globin mutation [IVS-I (?2) (A>C)]. Both patients had significant levels of Hb A, indicating that the IVS-I (?2) mutation is a relatively mild β⁺-thalassemia (β⁺-thal) allele. This mutation, in compound heterozygosity with Hb S, does not necessarily lead to a mild clinical course.     

Molecular Characterization of a β-Thalassemia Intermedia Patient Presenting Inferior Vena Cava Thrombosis: Interaction of the β-Globin Erythroid Krüppel-Like Factor Binding Site Mutation with Hb E and α+-Thalassemia

The molecular basis and hematological phenotype of adult Thai β-thalassemia intermedia (β-TI) patients encountered with inferior vena cava (IVC) thrombosis were investigated. Hematological and molecular analysis revealed a trait previously not described. The disease was caused by interaction of the β⁺-thalassemia (β⁺-thal) gene with the ?90 (C?>?T) (HBB: c.-140C?>?T) transition within the erythroid Krüppel-like factor (EKLF) binding site of the β-globin gene promoter with Hb E (HBB: c.79G?>?A) and α⁺-thalassemia (α⁺-thal). Hematological data of the patient were compared with those of heterozygous forms of these defects found in his family members and different genotype-phenotype interactions are illustrated. Globin gene haplotype analysis indicates an independent origin of this Thai β⁺-thal gene. Accurate diagnoses as well as knowledge of genotype-phenotype relationships were required for providing appropriate management of such cases.     

Combination of Hb Heze [β144(HC1)Lys→Arg; HBB: c.434A>G] and β0-Thalassemia in a Chinese Patient with β-Thalassemia Intermedia

We first report a novel β chain variant, Hb Heze [β144(HC1)Lys→Arg; HBB: c.434A>G], in a Chinese family. Heterozygous inheritance of the mutation results in a mild β-thalassemia (β-thal) phenotype, whereas compound heterozygosity of Hb Heze with β⁰-thal appears as the cause of β-thal intermedia (β-TI) in our case.     

Rare β-Globin Gene Mutations in Pakistan

The aim of this study was to analyze the rare β-thalassemia (β-thal) mutations in the Pakistani population. A total of 8716 unrelated Pakistani individuals having children with transfusion-dependent thalassemia were investigated by amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) for the previously reported common and rare β-thal mutations. Genomic sequencing of the β-globin gene and its immediate 5' and 3' flanking regions was done where no known mutation was found. Out of the 8716 individuals studied, 88 (1.0%) were not characterized by ARMS-PCR. Genomic sequencing revealed that 67 (0.82%) individuals had 19 different β-thal mutations including one novel mutation (HBB: c.136delT). The remaining 21 (0.26%) individuals did not show any mutation on the β-globin gene and its immediate flanking regions. The characterized alleles included seven (0.09%) in the 5' untranslated region (5'UTR), 29 (0.35%) in the coding regions, and 31 (0.38%) in the splice junction regions. HBB: c.92+1G>A and HBB: c.113G>A were the most frequently seen rare mutations. The spectrum of β-thal mutations in the Pakistani population is very diverse. In addition to the already reported mutations, another 19 different types of mutations were found. Interestingly, 21 individuals who had children with transfusion-dependent thalassemia and one known β-thal mutation, did not show any mutation on the β-globin gene. HBB: c.92+1G>A and HBB: c.113G>A are the most frequently seen rare mutations in Pakistan.     

Identification of a Novel Mutation in the β-Globin Gene 3′ Untranslated Region (HBB: c.*+118A > G) in Spain

Abstract

The 3′ untranslated region (3′UTR) region is well known to be associated with mRNA stability because of its associations with 3′ end processing, polyadenylation and mRNA capping. Mutations located in this area cause a β-thalassemia (β-thal) phenotype compatible with β⁺-thal. Two brothers, 49- and 41-years-old, were diagnosed with β-thal intermedia (β-TI) at 2 years of age. The β-globin gene from the promoter region to the 3′UTR was sequenced and both brothers were diagnosed to be compound heterozygotes for the 3′UTR +1592 (A?>?G) (HBB: c.*+118A?>?G) and codon 39 (C?>?T) (HBB: c.118C?>?T) mutations. Their mother was a carrier of the nonsense codon 39 mutation and her hematological data suggested β-thal trait; their father was a carrier of the 3′UTR +1592 mutation, though he did not have hematological parameters associated with β-thal. The adenine at position +1592 or +118 bases downstream of the termination codon is highly conserved among primates and placental mammals, as it is located between the polyadenylation A signal (PAS) and the polyadenylation A cleavage (PAC) sites. Given its location, it is likely that this mutation would interfere with mRNA maturation; however, the clinical data of the heterozygous carriers show virtually no significant alterations. Therefore, we suggest that the impact on cleavage-stimulation factor (CstF) recognition of the mRNA sequence would be minimal and not significantly alter polyadenylation. Although the mechanism is not known, and because the carrier has no β-thal minor, the mRNA is stable enough that the synthesis of the β-globin chain is unaffected.