Compound Heterozygote of Hb S (HBB: c.20A>T)/Hb Westdale (HBB: c.380_396delTGCAGGCTGCCTATCAG): Report of Four Cases from Odisha State,India

We report four cases of compound heterozygotes for Hb S (HBB: c.20A>T) and a rare β⁰-thalassemia (β⁰-thal) mutation, Hb Westdale (HBB: c.380_396delTGCAGGCTGCCTATCAG), characterized by a 17?bp deletion between codons 126 to 131 in exon 3 of the β-globin gene of human hemoglobin (Hb) confirmed by direct β-globin gene sequencing. All four cases were from four unrelated families belonging to the Agharia caste, an endogamous ethnic community of the Sundargarh and Jharsuguda districts of Odisha State, India. Detailed observations indicated that all four cases of Hb S/Hb Westdale were clinically severe. On family screening, six family members were found to be heterozygous for Hb Westdale and were asymptomatic. Deletional α-thalassemia (α-thal) and XmnI polymorphism were studied for all the Hb Westdale cases. The Hb S/Hb Westdale cases had an early median age at onset of symptoms and presentation, more requirement of blood transfusions, splenomegaly and hepatomegaly and were found to be clinically more severe when compared with the Hb S-β-thal with IVS-I-5 (G>C) (HBB: c.92?+?5G>C) cases. Overall, the findings indicate that this rare and hitherto unreported compound heterozygosity of Hb S/Hb Westdale is a clinically significant hemoglobinopathy and its finding in a large endogamous community of Odisha State, India will have important implication in the epidemiology and understanding of the clinical spectrum of sickle cell disease in Indian context and prenatal diagnosis.     

Hb Presbyterian (HBB: c.327C>G) in a Nicaraguan Family

Hemoglobin (Hb) is the protein responsible for oxygen transportation. It is a tetrameric protein comprising two α- and two β-globin subunits. In the literature, a large number of mutations in the α- and β-globin genes have been documented. Among these mutations, Hb Presbyterian (HBB: c.327?C>G), is a naturally occurring mutant exerting low oxygen affinity. The C to G exchange (AAC>AAG) at codon 108 of the β-globin gene results in the substitution of asparagine by lysine. Here, we document the identification of HBB: c.327?C>G in a 6-year-old female patient and her father from Nicaragua and Cuba, respectively. The presence of the abnormal Hb was confirmed by cellulose acetate electrophoresis, high performance liquid chromatography (HPLC) and genomic DNA sequencing. The β-globin gene sequences for both, father and daughter, disclosed the heterozygous mutation at codon 108 to be Hb Presbyterian or HBB: c.327?C>G. The mutant Hb was previously reported in four families from North America, Germany, Japan and Spain, respectively. This is the fifth family carrying HBB: c.327?C>G described to date and the first report from Latin America.     

Severe Drug-Induced Hemolysis in a Patient with Compound Heterozygosity for Hb Peterborough (HBB: c.334G>T) and Hb Lepore-Boston-Washington (NG_000007.3: g.63632_71046del)

Unstable hemoglobins (Hbs) are often overlooked in the differential diagnoses of drug-induced hemolysis. Hb Peterborough [β111(G13)Val→Phe; HBB: c.334G>T] is a rare unstable Hb variant, predominantly found in individuals of Italian descent, due to a structural defect involving a single amino acid substitution (phenylalanine for valine at position 111 of the β-globin chain). Unstable Hb variants are often inherited in the heterozygous state with Hb A (α2β2) and rarely in compound heterozygosity with other Hb variants. The presence of another variant Hb often alters the phenotype, occasionally resulting in more severe disease. Using a combination of molecular techniques; multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing, we identified a compound heterozygosity for Hb Peterborough and Hb Lepore-Boston-Washington (Hb LBW) [δ87, β116; NG_000007.3: g.63632_71046del] in a middle-aged gentleman with a history of chronic microcytic anemia and splenomegaly, presenting with severe drug-induced hemolysis, which was managed conservatively. The clinical history and presentation reflect the dual pathology due to the presence of two variant Hbs and their associated phenotypes. In this article, we discuss the phenotype resulting from the interaction of Hb Peterborough and Hb LBW and emphasize the importance of molecular testing in the diagnosis of rare Hb variants.     

Hb Stara Zagora: A New Hyper-Unstable Hemoglobin Causing Severe Hemolytic Anemia

We describe a new hyper-unstable β chain variant (codons 137–139, ? 6 bp) in a 2-year-old Bulgarian boy. The abnormal hemoglobin (Hb) is associated with severe hemolytic anemia as a consequence of its hyper instability. The child was admitted to the Pediatric Clinic (Faculty of Medicine, Stara Zagora, Bulgaria) at the age of 2 months. Because of anemia (Hb 6.9 g/dL) and high serum iron level (58 μM/L) the child was transfused. However, a month later his Hb level had dropped to 7.5 g/dL, and since then he has been on a regular monthly blood transfusion regimen. Hemoglobin analysis of a blood sample collected 2 months after the last transfusion at the age of 2 years, revealed no abnormalities except for the presence of inclusion bodies after incubation of peripheral blood with brilliant cresyl blue. Sequencing of the β-globin gene revealed heterozygosity for a 6 bp deletion (–TGGCTA) at codons 137 [the second and third base pair (bp)], 138 and 139 (the first bp), forming a new codon at position 137 (GAT). This event eliminates three amino acids (Val-Ala-Asn) and introduces a new residue (Asp). It creates a new restriction site for HphI. The parents and his dizygotic twin brother had no history of hemolysis. The paternity of the child was confirmed by DNA analysis.     

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.     

A Coincidental Discovery of a New Stable Variant (Hb Hachioji or HBB: c.187C>T) in a Patient with Chronic Hemolytic Anemia of Unexplained Origin

We report a new hemoglobin (Hb) variant, Hb Hachioji (HBB: c.187C>T), which was detected in a 32-year-old male with hemolytic anemia. The proband had undergone splenectomy in his childhood after being diagnosed with hereditary spherocytosis (HS) with no clinical improvement. A recent study showed that Heinz bodies were frequently observed in his red cells, however, no abnormal band was separated by isoelectric focusing (IEF), and the isopropanol (instability) test was negative. Direct sequencing revealed that the proband was a heterozygous carrier of a novel mutation (GCT>GTT) at codon 62 of the β-globin gene, leading to an alanine to valine substitution. This variant was named Hb Hachioji. Characterization at the mRNA level by cDNA sequencing detected β^Hachioji mRNA, as well as β^A mRNA. Subsequently, study of the proband’s family indicated that his father was a carrier of this Hb variant, although unexpectedly, the father was asymptomatic and clinically healthy. Oxygen affinity measurement of total Hb showed no alteration in the P₅₀ and oxygen equilibrium curve. The presence of Hb Hachioji was confirmed by mass spectrometry (MS). Hb Hachioji comprised approximately 50.0% of the total Hb and was a stable variant. The phenotypic discrepancy between these two carriers suggests that Hb Hachioji may not be associated with the hemolytic involvement in the proband. P4.2Nippon, which is the primary cause of most cases of Japanese HS, was absent in the proband’s parents. The coexistence of glucose-6-phosphate dehydrogenase (G6PD) deficiency was ruled out. Thus, the cause of hemolytic involvement in this patient remains unclear.     

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.     

Hb Iberia [α104(G11)Cys → Arg,TGC>CGC (α2) (HBA2:c.313T>C)], a New α-Thalassemic Hemoglobin Variant Found in the Iberian Peninsula: Report of Six Cases

We report a new structural defect of the α2-globin chain presenting with moderate microcytic hypochromic anemia, in six individuals from three unrelated families, living in Portugal and Spain. α-Globin gene deletions were ruled out by gap-polymerase chain reaction (gap-PCR) and multiplex ligation-dependent probe amplification (MLPA). Direct sequencing of the α2-globin gene revealed a substitution of codon 104 [α104(G11)Cys→Arg, TGC>CGC (α2) (HBA2:c.313T>C)]. This new variant, not detectable by high performance liquid chromatography (HPLC) or electrophoresis, was called Hb Iberia, as it was observed for the first time in families from the Iberian Peninsula.

Although the mutant allele is transcribed, as indicated by the balanced mRNA α/β ratio, the abnormal α2 chain could not form a stable tetramer as the cysteine and arginine residues, located at the α1β1 contact, differ in size, charge and hydrophobicity.

Hb Iberia is the third mutation described at codon 104 on the α-globin genes, namely, Hb Sallanches (α2, TGC>TAC) and Hb Oegstgeest (α1, TGC>AGC), also characterized as unstable hemoglobins (Hbs), present on an α-thalassemic phenotype.     

A HEMOGLOBIN VARIANT FOUND DURING GLYCOHEMOGLOBIN MEASUREMENT,IDENTIFIED AS Hb TOULON [α77(EF6)Pro→His] BY TANDEM MASS SPECTROMETRY

Hb Constant Spring [Hb CS, α142, Term→Gln, TAA>CAA (α2)] is a nondeletional form of α-thalassemia (α-thal) that is most prevalent in Southern Chinese and Southeast Asian populations. We previously found that Hb CS trait could efficiently be screened using Sebia Capillarys2. In this study, we report that Hb CS heterozygotes combined with β-thal could not be detected by the Sebia Capillarys2 method due to the very small amount of Hb CS.     

FOUR NEW β CHAIN HEMOGLOBIN VARIANTS WITHOUT CLINICAL OR HEMATOLOGICAL EFFECTS: Hb SAN BRUNO [β39(C5)Gln→His]; Hb FORT DODGE [β93(F9)Cys→Tyr]; Hb RHODE ISLAND [β116(G18)His→Tyr]; AND Hb INGLEWOOD [β142(H20)Ala→Thr]

Human Haemoglobin Variants and Their Characteristics H. Lehmann and P.A.H. Kynoch, Elsevier/North-Holland, Inc., New York, NY, 1976 vi+242 pages US $23.25/Df1.60.00 ISBN 0-7204-0585-8     

A New Hemoglobin Variant: Hb Izmir [β86(F2)Ala→Val,GCC>GTC; HBB:c.260C>T]

We report a new hemoglobin (Hb) variant [β86(F2)Ala→Val; HBB:c.260C>T] that we have named Hb Izmir. We have identified Hb Izmir in a Turkish woman by ion exchange high performance liquid chromatography (HPLC) during a premarital screening program in the Aegean region of Turkey. The mother and sister of the proband also carried the same variant. Using direct sequencing, we have characterized this variant as resulting from a GCC>GTC replacement at codon 86 of the β-globin chain, corresponding to an Ala→Val amino acid substitution. In the heterozygote, the level of Hb Izmir ranged from 41.38 to 45.6%. All heterozygotes had a Hb A₂ level of less than 3.5%. Total blood count values were normal and there were no other clinical findings. Although its clinical significance is thus far unclear, Hb Izmir may be important in hemoglobinopathy screening programs.     

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.     

Hb Penang [β78(EF2)Leu→Pro,HBB: c.236T>C]: a Novel β-Globin Variant

Abstract

We report a novel hemoglobin (Hb) variant with a β chain amino acid substitution at codon 78 (CTG>CCG) (HBB: c.236T>C), detected through prenatal screening via capillary electrophoresis (CE) in an otherwise healthy and asymptomatic 38-year-old female of Southeast Asian ancestry. The variant, named Hb Penang after the proband’s Malaysian city of origin, underwent further characterization through high performance liquid chromatography (HPLC), reversed phase HPLC, Sanger sequencing, isopropanol stability testing and isoelectric focusing (IEF).     

Hb Nebraska [β86(F2)Ala→Ile (HBB:c.259G>A;260C>T)]: A Unique High Oxygen Affinity Hemoglobin Variant with a Double Nucleotide Substitution within the Same Codon

A new high oxygen affinity hemoglobin (Hb) variant, Hb Nebraska [β86(F2)Ala→Ile, GCC>ATC; HGVS: HBB: c.259G>A;260C>T] is reported. This variant was not identified by routine methods and was only suspected due to erythrocytosis and an abnormal p50 value. The variant was analyzed by DNA sequencing and mass spectrometry (MS). The β chain variant is unusual in that it has two nucleotide substitutions occurring at the same codon.     

Coinheritance of Hb A2-Melbourne (HBD: c.130G>A) and Hb E (HBB: c.79G>A) in Laos and Simultaneous High Resolution Melt Detection of Hb A2-Melbourne and Hb A2-Lampang (HBD: c.142G>A) in a Single Tube

Abstract

We report the molecular and hematological identifications of a Hb A₂ variant [coinheritance of Hb A₂-Melbourne (HBD: c.130G>A) and Hb E (HBB: c.79G>A)] found for the first time in the Lao People’s Democratic Republic (PDR). The subject was a 29-year-old pregnant Laotian woman who was a foreign worker in Thailand and was diagnosed with thalassemia and hemoglobinopathies. Capillary electrophoresis (CE) demonstrated 1.6% of Hb A₂, with a minor unknown peak at the initial Z1 zone (1.7%). Identification of abnormal hemoglobin (Hb) using direct DNA sequencing showed a genetic defect causing a δ-globin gene missense mutation at codon 43 (GAG>AAG) causing a glutamic acid to lysine substitution corresponding to Hb A₂-Melbourne. The origin of Hb A₂-Melbourne in Lao PDR may be similar to a case found in Thailand with the [+ –?– –?– + +] haplotype. We developed a method that could clearly detect Hb A₂-Melbourne and Hb A₂-Lampang (HBD: c.142G>A) mutations in a single tube using high resolution melt (HRM) analysis. The HRM analysis is a more effective method for rapid detection than conventional polymerase chain reaction (PCR), as there is no need for a post-PCR step, and no exposure to ethidium bromide. This new method would be a useful addition for the first investigation of a suspected Hb A₂ variant in the routine molecular setting.     

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 S-San Martin: A New Sickling Hemoglobin With Two Amino Acid Substitutions [β6(A3)Glu→Val;β105(G7)Leu→Pro] In An Argentinean Family

A new sickling hemoglobin (Hb) detected in an Argentinean family from San Martín, Buenos Aires, Argentina, is hereby described. Two mutations were identified on the same β-globin gene resulting in a new variant named Hb San Martin. One mutation was found on exon 1, corresponding to Hb S [β6Glu→Val, GAG>GTG] and the second one on exon 3 at β105(G7)Leu→Pro, CTC>CCC. The replacement of leucine by proline will likely impair the structure breaking helix G and causing instability of the molecule and the clinical manifestations typical of unstable Hbs. The mutation at β105 seemed to be a de novo one in our patients, arising on a previously mutated gene, due to the fact that Hb S is the most frequent structural variant.     

Hb Calais [β76(E20)Ala→Pro]: A Family Study of a Variant With Decreased Oxygen Affinity

Secondary to the detection of a chronic anemia with a slightly increased Hb F level in a 7‐year-old boy carrying a hemoglobin (Hb) variant, we investigated the members of his family and found that they were related to the original case of Hb Calais. In the present study, we report the clinical and biological impacts of this Hb variant in various members of three generations of this family.     

Compound Heterozygosity for an Unstable Novel Hemoglobin Variant,Hb Dongguan [α52(E1)Ser→Cys (TCT>TGT); HBA1: c.158C>G], and the – –SEA (Southeast Asian) α-Thalassemia Deletion

Abstract

Here we report a 67-year-old Chinese male carrying an unstable novel hemoglobin (Hb) variant in compound heterozygosity with the – –^SEA (Southeast Asian) α-thalassemia (α-thal) deletion. Hemoglobin analysis by capillary electrophoresis (CE) revealed a rapid degradation feature of the variant. Sanger sequencing of the Hb gene revealed a novel homozygous mutation in exon 2 of the α1-globin gene [α52(E1)Ser→Cys (TCT>TGT); HBA1: c.158C>G]. We named this novel variant Hb Dongguan for the place of origin of the proband. Additionally, gap-polymerase chain reaction (gap-PCR) indicated the presence of the heterozygous – –^SEA α-thal deletion.