Identification of a New HBA1 Gene Mutation (HBA1:c.301-2A>T) in Cis with Hb Riccarton (HBA1:c.154G>A) [α51(CE9)Gly→Ser

We report two point mutations found in a heterozygous state on the HBA1 gene of an 88-year-old Argentinean patient with an α(+)-thalassemia (α(+)-thal) phenotype: Hb Riccarton HBA1:c.154G>A) [α51(CE9)Gly→Ser] and a novel mutation, HBA1:c.301-2A>T that affects the splicing acceptor site of the second intron and leads to a non functional α-globin chain. Cloning of the HBA1 PCR (polymerase chain reaction) product and direct sequencing of the clones revealed that both mutations were in cis.     

Novel Mutation of the Translation Initiation Codon of the α1-Globin Gene (ATG>AAG or HBA1:c.2T>A)

We report two Italian–Canadian families with α⁺-thalassemia (α⁺-thal) trait caused by a novel mutation of the translation initiation codon of the α1-globin gene (ATG>AAG or HBA1:c.2T>A). This is the tenth reported α-thal mutation involving the translation initiation codon or the conserved Kozak consensus sequences of the HBA2 or HBA1 genes.     

A Unique Interaction of IVS-I-1 (G>A) (HBA2: c.95+1G>A) with Hb Adana (HBA2: c.179G>A) Presenting as Transfusion-Dependent α-Thalassemia

Abstract

Nondeletional α-globin mutations are known to cause more serious clinical effects than deletional ones. A rare IVS-I-1 (G>A) (HBA2: c.95+1G>A) donor splice site mutation interferes with normal splicing of pre mRNA and results in activation of a cryptic splice site as well as a frameshift mutation. Hb Adana [HBA2: c.179G>A (or HBA1)] is a highly unstable variant hemoglobin (Hb) resulting from a mutation at codon 59 on the HBA2 or HBA1 gene, recognized to cause severe α-thalassemia (α-thal) syndromes. We report a unique case of compound heterozygosity for these two mutations in a 9-year-old boy who presented with a Hb level of 5.3?g/dL and hepatomegaly at the age of 15?months. He required regular blood transfusions in view of a Hb level of <7.0?g/dL and failure to thrive. He had thalassemic red cell indices and peripheral blood film. The Hb electrophoresis only showed a raised Hb F level (3.3%) and a pre run peak but the Hb H inclusion test was negative. His father had thalassemic red cell indices but a normal Hb level. His mother had almost normal Hb levels and red cell indices. Hb Adana involving the HBA2 gene was detected by mutiplex amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) in the proband and his father. DNA sequencing of the HBA2 gene confirmed the IVS-I-1 mutation in the proband and his mother. This case highlighted the unique interaction of the IVS-I-1 mutation with Hb Adana in a young Malay boy presenting with transfusion-dependent α-thal.     

Double Heterozygosity for Hb Durham-N.C. (HBB: c.344T>C) [β114(G16)Leu→Pro] and the IVS-I-110 (HBB: c.93-21G>A) Causing a Severe β-Thalassemia Phenotype

Abstract

The evaluation of a 10-month-old girl of Sicilian origin with a clinical phenotype of severe thalassemia led to the identification of two β-globin gene defects, a β-thalassemia (β-thal), mutation at IVS-I-110 (HBB: c.93-21G>A) and a variant hemoglobin (Hb) mutation at codon 114 (HBB: c.344T>C) on the other allele, reported as Hb Durham-N.C. (also known as Hb Brescia) [β114(G16)Leu→Pro] in the HbVar database. A very low Hb level (Hb 3.5?g/dL), microcytosis [mean corpuscular volume (MCV) 63.2 fL] and hypocromia [mean corpuscular Hb (MCH) 19.6?pg], increased red blood cell (RBC) distribution width (RDW) (36.0%), higher reticulocytes (6.2%), anisocytosis, poikilocytosis, hypocromia, basophilic stippling and inclusion body formation, were present in the affected subject. Analysis of other family components showed the presence of HBB: c.93-21G>A defect in the mother and in her brother, while Hb Durham-N.C. was absent in all other relatives, thus, this mutation has arisen as a de novo defect. This is the first case described as a severe thalassemic phenotype in a compound heterozygote carrier of this unstable Hb and a common β-thalassemic allele. The important information gained from this case is that a rare dominant or recessive mutation may arise in every individual, even if this is a very rare event.     

Complex Interaction of Hb Q-Thailand (HBA1: c.223G>C) with β-Thalassemia/Hb E (HBB: c.79G>A) Disease

Hb Q-Thailand [α74(EF3)Asp→His (α1), GAC>CAC, HBA1: c.223G>C] is an abnormal hemoglobin (Hb) frequently found in Thailand and Southeast Asian countries. The association of the α^Q-Thailand allele with other globin gene disorders has important implications in diagnosis. Here, we report how to diagnose the coinheritance of Hb Q-Thailand with β-thalassemia (β-thal)/Hb E disease in four Thai samples from high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) testing results. Understanding of the HPLC chromatogram and CE electropherogram patterns of this complex mutation is important for interpretation of testing results and providing genetic counseling.     

Two new hemoglobin variants: Hb Aix-Les-Bains [β5(A2)Pro→Leu; HBB:c.17 C>T] and Hb Dubai [α122(H5)His→Leu (α2); HBA2:c.368 A>T

We report two new hemoglobin (Hb) variants; one causing an impairment of the N-terminal glycation of the β-globin chain and the other a hematological phenotype of α-thalassemia (α-thal). The first variant is Hb Aix-les-Bains [β5(A2)Pro→Leu] and the second Hb Dubai [α122(H5)His→Leu (α2)]. These two new Hb variants were detected by chromatographic and electrophoretic methods and characterized by molecular studies. Hb Dubai gives an α-thalassemic phenotype and should be routinely detected for preventing severe Hb H disease in couples at-risk for α-thal.     

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.     

Two New γ Chain Variants: Hb F-Augusta GA [Gγ59(E3)Lys → Arg; HBG2: c.179A > G] and Hb F-Port Royal-II [Aγ125(H3)Glu → Ala; HBG1: c.377A > C]

The total number of hemoglobin (Hb) variants so far reported to the HbVar database is 1598 (April 9 2014) and 130 of them are fetal Hb variants. Fetal Hb are categorized as two different subunits, ^Gγ- and ^Aγ-globin chains, and γ chain variants can be observed in both subunits. There are 72 ^Gγ- and 58 ^Aγ-globin chain variants. Most of them are clinically silent and detected during newborn screening programs in the USA and outside the USA. In this report, we discuss the molecular characteristics and diagnostic difficulties of two new γ-globin chain variants found in an African American baby with no clinical symptoms. One is a new ^Gγ-globin chain variant, Hb F-Augusta GA [^Gγ59(E3)Lys?→?Arg; HBG2: c.179A?>?G] and the other one is Hb F-Port Royal-II [^Aγ125(H3)Glu?→?Ala; HBG1: c.377A?>?C].     

Description of a rare β-globin gene mutation,IVS-II-848 (C>A) (HBB: c.316-3C>A) in association with IVS-I-1 (G>A) (HBB: c.92 + 1G>A), observed in a Syrian family: a case report

Abstract

β-Thalassemia (β-thal) is a hereditary and heterogeneous group of disorders caused by mutations on the β-globin gene that result in the reduced or non production of β-globin chains. We report a rare β-globin mutation, IVS-II-848 (C>A) (HBB: c.316-3C>A), which was found in a female Syrian patient. This mutation was associated with the IVS-I-1 (G>A) (HBB: c.92+1G>A) mutation, and the genotype is a compound heterozygote for IVS-I-1(G>A)/IVS-II-848(C>A). This combination was found for the first time in Syria.     

A New δ Chain Variant,Hb A2-Tunis [δ46(CD5)Gly → Glu; HBD: c.140G>A], Observed in a Tunisian Family in Association with a Compound Heterozygosity for Hb C [β6(A3)Glu → Lys; HBB: c.19G>A] β0-Thalassemia [IVS-I-1 (β143, G>A); HBB: c.92+1G>A]

We describe a new δ-globin variant, Hb A₂-Tunis [δ46(CD5)Gly?→?Glu; HBD: c.140G>A]. This hemoglobin (Hb) variant displayed a faster electrophoretic mobility than normal Hb A₂ and was expressed at 3.2%. The molecular defect was characterized by DNA sequencing analysis. Hb A₂-Tunis was found in a carrier of a β⁰-thalassemia (β⁰-thal) [IVS I-1 (β143, G>A); HBB: c.92?+?1G>A] and Hb C [β6(A3)Glu?→?Lys; HBB: c.19G>A], presenting with a normal Hb A₂ level. Phenotype and genotype investigations revealed that the patient has a total Hb A₂ level of 7.1% that was expected for a β-thalassemia (β-thal) minor carrier.     

Hb Midnapore [β53(D4)Ala→Val; HBB: c.161C>T]: A Novel Hemoglobin Variant with a Structural Abnormality Associated with IVS-I-5 (G>C) (HBB: c.92+5G>C) Found in a Bengali Indian Family

We describe a novel C>T substitution at codon 53 of the HBB gene (HBB: c.161C>T). The proband was a transfusion-dependent β-thalassemia major (β-TM) patient. DNA was extracted and subsequently, DNA sequencing was done to detect the mutations on the HBB gene. Capillary zone electrophoresis (CZE) revealed the presence of an unknown peak. She inherited this mutation from her grandmother through her mother. This mutation exists in cis with the common β⁰ mutation IVS-I-5 (G>C) (HBB: c.92+5G>C). The proband is homozygous for HBB: c.92+5G>C and needs monthly transfusions. On the other hand, her grandmother, mother and sister all possess this novel mutation cis with the heterozygous HBB: c.92+5G>C. They are carriers not thalassemic. This mutation produces the substitution β53(D4)Ala→Val; HBB: c.161C>T, a new structural hemoglobin (Hb) variant. As this variant was identified in a Bengali family from Paschim Midnapore district of West Bengal, India, it has been designated as Hb Midnapore. This variant has now been reported to the HbVar database.     

A New Hemoglobin Variant: Hb Henan [β90(F6)Glu → Gln; HBB: c.271G < C]

We have identified a new β chain hemoglobin (Hb) variant in a Chinese individual. Sequencing of the β-globin gene revealed a mutation in exon 2 at nucleotide 271, which results in the replacement of a glutamic acid by glutamine at codon 90 [β90(F6)Glu?→?Gln; GAG?>?CAG; HBB: c.271G?>?C] that we have named Hb Henan.     

Compound Heterozygosity for Silent Cap +1570 (T>C) (HBB: c*96T>C), Codon 39 (C>T) (HBB: c.118C>T) and the Presence of αααanti–3.7/αα in Greece. A Case Presentation

Abstract

The rare point mutation Cap +1570 (T>C) (HBB: c*96T>C) has been reported in families of Czech, Greek, Turkish and Italian origin. The mutation contributes to a reduction of the β-globin chain synthesis, and in heterozygous carriers, it causes a silent phenotype, while in compound heterozygosity with severe β-thalassemia (β-thal) mutations, it leads to a non transfusion dependent β-thal intermedia (β-TI) state. We report a case of compound heterozygosity for codon 39 (C>T) (HBB: c.118C>T) and Cap +1570, in addition to the presence of ααα^anti–3.7/αα.     

Severe Thalassemia Caused by Hb Zunyi [β147(HC3)Stop→Gln; HBB: c.442T>C)] on the β-Globin Gene

Hemoglobinopathies are caused by genetic defects on the globin genes. To date, more than 900 β-globin variants have been recorded worldwide. These gene alterations often cause either a decrease in β-globin synthesis or completely block synthesis, leading to a hemoglobinopathy. While most of these causative mutations are inherited, de novo mutations are quite rare. Here, we investigated three hemoglobinopathy cases. These patients developed severe hemolytic anemia at 3-5?months of age and were transfusion-dependent. In patient 1, a novel β variant, Hb Zunyi [β147(HC3)Stop→Gln; HBB: c.442T>C] was identified. This de novo mutation results in a stop codon substitution to a glutamine residue at codon 147 of the β-globin gene, and leads to severe thalassemia. In patient 2, we discovered the rare Hb Southampton mutation [β106(G8)Leu→Pro; HBB: c.320T>C], while in patient 3, the rare Hb Alesha mutation [β67(E11)Val→Met (GTG>ATG); HBB: c.202G>A] was detected. The identification of the novel β variant, Hb Zunyi, has added to the human globin database and will shed light on future diagnosis of hemoglobinopathy/thalassemia and genetic counseling.     

Hb Agenogi [β90(F6)Glu→Lys (GAG>AAG) HBB: c.271G>A)] in a Pregnant Thai Woman

Hb Agenogi [β90(F6)Glu→Lys (GAG>AAG) HBB: c.271G>A)] is a very rare β-globin chain variant. We report for the first time this hemoglobinopathy in a pregnant 20-year-old Thai woman. She was seen by an obstetrician at her 14th week of gestation. She was pale and had an inflammatory lesion of her lower left leg. The hemoglobin (Hb) analysis by high performance liquid chromatography (HPLC) and low pressure liquid chromatography (LPLC) showed a peak of abnormal Hb at the C window. On capillary electrophoresis (CE), the abnormal Hb peak was observed at electrophoretic zone 4 that corresponded to the Hb E (HBB: c.79G>A) peak. Direct DNA sequencing revealed a GAG>AAG mutation at codon 90 of the β-globin gene. Thus, even though Hb Agenogi is very rare, it can be found in Thai people. The knowledge and understanding of this hemoglobinopathy will be used to assist in diagnosis, management and counseling for patients.     

Severe α-Thalassemia Intermedia Due to a Compound Heterozygosity for the Highly Unstable Hb Adana (HBA2: c.179G>A) and a Novel Codon 24 (HBA2: c.75T>A) Mutation

We report a novel mutation at codon 24 of the α2-globin gene (HBA2: c.75T?>?A) found in a Sundanese family. This novel mutation was detected during prenatal diagnosis. The couple already had a 7-year-old boy who exhibited clinically severe α-thalassemia intermedia (α-TI), and he was found to be a compound heterozygote for the novel mutation at codon 24 and the previously described Hb Adana (HBA2: c.179G?>?A) at codon 59 of the α2-globin gene. The father was a carrier of the novel point mutation and showed normal hemoglobin (Hb) and a low mean corpuscular volume (MCV) and mean corpuscular Hb (MCH) value.     

Hb Oslo [β42(CD1)Phe→Ile; HBB: c.127T>A]: A Novel Unstable Hemoglobin Variant Found in a Norwegian Patient

Unstable hemoglobin (Hb) variants are the result of sequence variants in the globin genes causing precipitation of Hb molecules in red blood cells (RBCs). Intracellular inclusions derived from the unstable Hb reduce the life-span of the red cells and may cause hemolytic anemia. Here we describe a patient with a history of hemolytic anemia and low oxygen saturation. She was found to be carrier of a novel unstable Hb variant, Hb Oslo [β42(CD1)Phe→Ile (TTT>ATT), HBB: c.127T>A] located in the heme pocket of the β-globin chain. Three-dimensional modeling suggested that isoleucine at position 42 creates weaker interactions with distal histidine and with the heme itself, which may lead to altered stability and decreased oxygen affinity. At steady state, the patient was in good clinical condition with a Hb concentration of 8.0–9.0?g/dL. During virus infections, the Hb concentration fell and on six occasions during 4 years, the patient needed a blood transfusion.     

β+-Thalassemia trait due to a novel mutation in the β-globin gene promoter: -26 (A>C) [HBB c.-76A>C

We report the case of a woman with β(+)-thalassemia (β(+)-thal) trait, in which there were two sequence variants within the β-globin gene promoter: -54 (G>A) [HBB c.-104G>A] and -26 (A>C) [HBB c.-76A>C]. Data from other patients indicate that the -54 substitution is a non pathogenic sequence variant. Therefore, the β-thal phenotype is most likely due to the -26 mutation that is adjacent to the conserved ATAA box.