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.     

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.     

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.     

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.     

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.     

Homozygosity for HBA1: c.179G > A: Hb Adana in an Infant

Hb Adana (HBA1: c.179G?>?A) is a very rare, unstable form of α-globin variant that results from deficient synthesis of functional α chains. We present a 2-month-old boy with hypochromic microcytic anemia, and remarkable anisocytosis, target cells and basophilic stippling on his peripheral blood smear. α-Globin gene analysis of the patient determined homozygosity for HBA1: c.179G?>?A, a mutation known as Hb Adana. On his follow-up visit, hemoglobin (Hb) levels were stable at 9.0–9.5?g/dL and mean corpuscular volume (MCV) was 62.2–62.5?fL without the need for a blood transfusion. Clinical and hematological findings of our case were comparable to Hb H (β4) or β-thalassemia intermedia (β-TI)-like phenotypes, despite the fact that he carried an α1 gene mutation. Heterozygosity for the HBA1: c.179G?>?A mutation may also lead to microcytosis only as seen in his parents. According to our current knowledge, this is the first described case with homozygosity for the Hb Adana mutation, carried on the α1 gene. The relatively mild presentation of the case highlights the milder phenotypic consequences of nondeletional α mutations in the α1 vs. the α2 gene.     

A Case Series of α-Thalassemia Intermedia Due to Compound Heterozygosity for Hb Adana [HBA2: c179G>A (or HBA1); p.Gly60Asp] With Other α-Thalassemias in Malay Families

Hb Adana [HBA2: c179G>A (or HBA1); p.Gly60Asp] is a rare hemoglobin (Hb) variant due to a mutation at codon 59 of the α2- or α1-globin gene resulting in a glycine to aspartic acid substitution. Two siblings with a unique coinheritance of Hb Adana and Hb Constant Spring (Hb CS, α142, Term→Gln, TAA>CAA; HBA2: c.427?T>C) (α^{codon 59}α/α^CSα), were compared phenotypically with another two siblings carrying the Hb Adana mutation and a 3.7?kb deletion (α^{codon 59}α/?α^3.7). Although they all had α-thalassemia intermedia (α-TI), the former were clinically more severe than the latter. The first pair of siblings presented at a much younger age than the second pair and showed lower Hb levels and significant extramedullay hemopoiesis. Another case of a hydropic fetus as a result of Hb H/Hb Adana is also described. Their clinical phenotypes and hematological parameters are all presented for comparison.     

Hb A2-Tianhe (HBD: c.323G>A): First Report in a Chinese Family with Normal Hb A2-β-Thalassemia Trait

Coinheritance of δ-globin variants along with β-globin gene defects can interfere with correct diagnosis of β-thalassemia (β-thal) trait. In this report, we present the coinheritance of a δ-globin variant, Hb A₂-Tianhe [δ107(G9)Gly→Asp; HBD: c.323G>A] and a heterozygous β-thal in a Chinese individual with microcytosis, hypochromia and a normal Hb A₂ level.     

FBN1基因c.7708G>A突变致马方综合征2例及文献复习

<正>马方综合征（Marfan syndrome, MFS）是由FBN1基因突变引起的多系统受累的常染色体显性遗传病,以主动脉根部动脉瘤/夹层、晶状体异位和骨骼畸形为特征,是早发性胸主动脉夹层的重要病因。本文报道了FBN1基因第62号外显子c.7708G>A突变的一家MFS母子的临床诊治,并对报告了该位点突变的文献进行复习,旨在帮助临床医师提高对MFS的认识。     

A Novel α-Thalassemia Nonsense Mutation on the α2-Globin Gene: HBA2: c.184A>T

We report a novel mutation on the α2-globin gene, HBA2: c.184A>T, detected in a Chinese proband. This mutation resulted in a Lys→Term substitution at position 62 of the α2-globin gene, causing a premature termination of translation. This mutation did not cause severe hematological abnormalities in the carriers. From the properties of substituted residues on the α2-globin gene, it is generally expected that this mutation causes unstable and truncated protein, thus this mutation should be detected in couples at-risk for α-thalassemia (α-thal).     

Hb Savaria [α49(CE7)Ser→Arg; HBA2: c.150C > A]: A New Case and Complete Description

Hb Savaria [α49(CE7)Ser→Arg; HBA2: c.150C?>?A] is a rare hemoglobin (Hb) variant, initially described in Eastern Europe but present worldwide. It belongs to that class of variants which can be confused with Hb S [β6(A3)Glu→Val; HBB: c.20A?>?T] by automated protein analysis and thus needs special tests for proper identification. Because it could arise from different nucleotide substitutions and according to the rules of the Human Genome Variation Society (HGVS) nomenclature, three ‘Hb Savaria’ variants are possible. In the case reported here it resulted from the HBA2: c.148A?>?C change.     

Compound Heterozygote for a Novel Elongated C-Terminal β-Globin Variant (HBB: c.364delG) and Hb E (HBB: c.79G>A) with Heterozygous α-Thalassemia-2

This study reports the case of 2-year-old Northeastern Thai girl with β-thalassemia (β-thal) disease who has required regular blood transfusions since she was 8?months old. Hemoglobin (Hb) analysis by high performance liquid chromatography (HPLC) separated Hb A₂/E (16.5%), Hb F (22.7%), Hb A (51.8%) and an abnormal peak (Hb X) found at a retention time (RT) of 5.05?min. (C-window) with 2.8%. Multiplex gap-polymerase chain reaction (gap-PCR) revealed heterozygous α-thalassemia-2 (α-thal-2) (–α^3.7/αα; NG_000006.1: g.34164_37967 del3804). This patient was suspected of having a β-globin chain variant and Hb E (HBB: c.79G>A) according to the high Hb F level and disease presentations. Surprisingly, Hb Mahasarakham (the geographic origin of the proband), a novel single nucleotide deletion (–G) at the first nucleotide of codon 121 (HBB: c.364delG), was identified by direct DNA sequencing and secondary confirmation by PCR-restriction fragment length polymorphism (PCR-RFLP). This novel mutation causes a frameshift mutation and added 10 more residues to the β-globin chain that was elongated to 156 amino acids. Molecular basis of this novel mutation in the heterozygous state is required to confirm the mode of inheritance.     

Hb Tarrant [α126(H9)Asp→Asn; HBA2: c.379G > A (or HBA1)] in a Chinese Family as a Cause of Familial Erythrocytosis

Hb Tarrant [α126(H9)Asp→Asn; HBA2: c.379G?>?A (or HBA1)], is a rare high oxygen affinity hemoglobin (Hb) variant that causes erythrocytosis, previously described in a few Mexican–American families. Here we report the first Chinese family with this Hb variant presenting with unexplained familial erythrocytosis. No evidence of hemolysis was seen. A locally adapted approach to the diagnostic process in clinical laboratories is discussed. Molecular analysis has an important role in confirmation of the diagnosis. Proper identification of this rare but clinically significant Hb variant is helpful for family counseling and will help to guide appropriate management of absolute erythrocytosis.     

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.     

Hb Grifton [α87(F8)His→Pro; HBA1: C.263A > C (or HBA2)] Causes Abnormal Pulse Oximetry Measurements

An asymptomatic toddler and his mother consistently demonstrated low transcutaneous pulse oximetry (SpO2) measurements, discordant with normal arterial blood gas analyses while breathing room air. Previous evaluations by medical teams were unable to identify an etiology of their perceived hypoxia. Further investigation revealed that the boy carried an abnormal variant, Hb Grifton or α87(F8)His→Pro; HBA1: c.263A?>?C (or HBA2), discovered on newborn screening, which was not suspected as the underlying cause of his abnormal pulse oximetry readings until an inpatient admission to our hospital for asymptomatic “hypoxia,” where he was found to share these same characteristics with his mother. We showed that a difference in light absorption between the oxygenated Hb Grifton variant and oxygenated Hb A resulted in erroneous pulse oximetry values. This phenomenon has previously been reported in a handful of other variant Hbs. Astute clinical suspicion, in conjunction with laboratory testing leading to correct diagnoses of variant Hbs, may prevent expensive work-ups and unnecessary medical treatments for asymptomatic patients falsely presumed to be hypoxemic based on low pulse oximetry measurements.     

Molecular Analysis of β-Thalassemia Patients: First Identification of Mutations HBB:c.93-2A>G and HBB:c.114G>A in Brazil

The various clinical phenotypes in β-thalassemias have stimulated the study of genetic factors that could modify the manifestations of these diseases. We examined 21 patients with β-thalassemia (β-thal) in order to identify some genetic modifying factors: β-thalassemia mutations, HBG2:g.–158C>T polymorphism, α-globin gene deletions and (AT)xNz(AT)y motif within the hypersensitive site 2-locus control region (HS2-LCR). In the 42 alleles analyzed, the most frequent mutations observed were HBB:c.92+6T>C (30.9%), HBB:c.118C>T (16.7%), HBB:c.93-21G>A (11.9%) and HBB:c.92+1G>A (4.8%); this finding is in accordance with previous data of the Brazilian population. The other genetic factors analyzed showed no relation with the severity of the disease. For the first time in Brazil, we report HBB:c.93-2A>G and HBB:c.114G>A mutations on the β-globin gene, both in a heterozygous state. This is also the first study to analyze the HS2-LCR in β-thalassemic individuals in the Brazilian population.     

Molecular analysis of β-thalassemia patients: first identification of mutations HBB:c.93-2A>G and HBB:c.114G>A in Brazil

The various clinical phenotypes in β-thalassemias have stimulated the study of genetic factors that could modify the manifestations of these diseases. We examined 21 patients with β-thalassemia (β-thal) in order to identify some genetic modifying factors: β-thalassemia mutations, HBG2:g.-158C>T polymorphism, α-globin gene deletions and (AT)xNz(AT)y motif within the hypersensitive site 2-locus control region (HS2-LCR). In the 42 alleles analyzed, the most frequent mutations observed were HBB:c.92+6T>C (30.9%), HBB:c.118C>T (16.7%), HBB:c.93-21G>A (11.9%) and HBB:c.92+1G>A (4.8%); this finding is in accordance with previous data of the Brazilian population. The other genetic factors analyzed showed no relation with the severity of the disease. For the first time in Brazil, we report HBB:c.93-2A>G and HBB:c.114G>A mutations on the β-globin gene, both in a heterozygous state. This is also the first study to analyze the HS2-LCR in β-thalassemic individuals in the Brazilian population.     

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.