Clinically relevant updates of the HbVar database of human hemoglobin variants and thalassemia mutations

Hb H disease associated with compound heterozygosity for --SEA deletion and a novel alpha globin chain variant (HBA2:c.175C>A) on the distal histidine in a Chinese family

OBJECTIVES

In clinical practice, the majority of α-thalassaemia cases arise from deletions of the α-globin genes. However, a subset of cases is attributed to rare haemoglobin variants, which can manifest with borderline or normal screening results, potentially leading to missed diagnoses in clinical practice.

METHODS

Blood samples were collected from family members and underwent haematological, DNA and RNA analysis.

RESULTS

The five-month-old proband presented a haematological phenotype consistent with Hb H disease. The mother's haematology profile was consistent with an α-thalassaemia carrier, while the father exhibited a borderline reduction in MCV and MCH. MALDI-TOF identified an abnormal α-chain in the proband. DNA analysis revealed a novel α-globin variant (HBA2:c.175C>A, α58His>Asn, Hb DG-Nancheng) affecting the distal histidine in the family. The father and the mother had α-genotype of --SEA/αα and αDG-Nanchengα/αα, respectively; while the proband inherited both mutant alleles (--SEA/αDG-Nanchengα). Sequencing of cDNA from HBA2 gene identified an equal ratio of normal and mutant alleles.

CONCLUSION

This rare case highlighted the importance of identifying rare haemoglobin variant during prenatal screening. The clinical and genetic data provides useful information on the pathogenicity of this variant and further insight into the role of distal histidine residue of α-globin.

A Novel 165 Kb Duplication Involving the α-Globin Gene Cluster Is Identified by Low-Pass Whole Genome Sequencing in a Chinese Thalassemia Intermedia Patient

Copy number variations (CNVs) involving the α-globin gene cluster can lead to an imbalance in the proportion of α- and β-globin chains and consequently cause clinical symptoms of β-thalassemia. In our case, a 6-year-old boy, clinically diagnosed with β thalassemia intermedia, was admitted for further genetic diagnosis with his family. Targeted sequencing and third generation sequencing (TGS) were used to detect the possible variants of the thalassemia genes. Low-pass whole genome sequencing (lpWGS) was conducted to specify the exact location of relevant CNVs across the genome, which was then validated by multiplex ligation-dependent probe amplification.The results revealed that the patient had a heterozygous β0 mutation of Codon17 (A > T) and a full duplication of the α-globin gene cluster, inherited from his mother and father, respectively. Besides, a novel point mutation within the 5' untranslated region of β-Globin (HBB: c. -175 (G > A) was only detected in the patient. This study suggests that lpWGS seems a powerful alternative to detect large CNVs related to thalassemia with second intention for more information of the breakpoints and a simultaneous genome-scale detection of other pathogenic CNVs.

A Novel Frameshift Mutation(HBA2:C.337delC) Associated With α-Thalassemia Trait Detected by Next-Generation Sequencing in Southern China

Here, we report a novel frameshift mutation caused by a single base deletion in exon 3 of the HBA2 gene (HBA2:c.337delC) detected by next-generation sequencing. The proband was a 26-year-old Chinese pregnant woman who originates from Hunan Province. Her mean corpuscular volume(MCV) and mean corpuscular hemoglobin (MCH) had a mild decrease. Capillary electrophoresis (CE) showed that both Hb A (97.8%) and Hb F (0.0%) values were within normal range, while the Hb A2 (2.2%) value was below normal. Sequence analysis of the α and β-globin genes revealed a novel single base deletion at codon 112 (HBA2:c.337delC) in the heterozygous state, which resulted in a mild phenotype of α-thalassemia.

The First Iranian Case of Unstable Hemoglobin Santa Ana

In this report, we describe a 6-year-old girl with a medical history of pallor, mild icterus, anemia, blood transfusion and abnormal hemoglobin variant analysis on capillary electrophoresis. She was referred for further analysis. DNA sequencing of the proband revealed a de novo mutation in Codon 88 (CTG > CCG) of the β-globin gene (HBB: c.266T > C) in a heterozygous state compatible with hemoglobin Santa Ana, an unstable hemoglobin. This is the first case of Hb Santa Ana from Iran associated with moderate to severe anemia who underwent splenectomy with clinical improvement.

Haemoglobin Ottawa, sickle cell trait and vaso-occlusive crises

A girl with a sickle cell trait had severe VOCs (vaso-occlusive crises), her father also had a sickle cell trait but mild VOCs, and her mother had no symptoms. Electrophoresis on agarose gel under alkaline conditions showed haemoglobin AS (HbAS) in the girl and in her father, with an S band increased more than expected (46.2% and 41.2% respectively), and a band migrating at C (16.8% and 8.9% respectively) in both. There was a band at S (19.6 %) in her mother. The C band was attributed to a hybrid tetramer with haemoglobin S (HbS) and a Hb variant. A homozygous c.46G>C mutation (Hb Ottawa, the Hb variant) was detected by Sanger sequencing in the girl. Heterozygosity for Hb Ottawa by Sanger sequencing was shown in both the father and the mother. The father, with HbAS and heterozygous for Hb Ottawa, had mild VOCs. Heterozygosity only for Hb Ottawa did not produce any abnormality in the mother. A sister and two brothers of the index patient presented a Hb variant, probably Hb Ottawa, migrating to the S zone (all 20%) at electrophoresis, without HbS. These last three were asymptomatic. We conclude that Hb Ottawa, an α-globin variant, contributes along with haemoglobin S (HbS) to VOC symptoms.

First Report of Filipino β0-Thalassemia/β-Thalassemia in a Chinese Family

A pregnant woman living in Fujian Province, southeastern China, presented due to a risk of having a baby with β-thalassemia major, during her second pregnancy, since she and her husband were suspected as β-thalassemia carriers and their affected daughter was a transfusion-dependent patient. Using the common α-thalassemia and β-thalassemia genotypes test, the pregnant woman was diagnosed as a β-thalassemia carrier with βIVS-2 - 654 (C→T)/βN genotype and her daughter had a homozygosity for IVS - 2 - 654 (C→T) mutation, however, no abnormalities were detected in her husband. SMRT identified a Filipino β0-deletion in her husband, and MLPA also revealed an unknown deletion in the HBB gene. Electrophoresis showed approximately 350 bp of the PCR product, and the β-Filipino genotype presented novel fracture fragments ranging from 5,112,884 to 5,231,358 bp, and lacked a 118,475 bp fragment relative to the wild-type sequence. The daughter was therefore diagnosed with the βIVS-2 - 654 (C→T)/βFilipino genotype. Prenatal diagnosis with umbilical cord blood at 27th week of gestation showed heteroztgosity for IVS - 2 - 654 (C→T) mutation in the fetus and continued pregnancy was recommended. In conclusion, we identified the Filipino β0-deletion in a Chinese family, from Fujian area, for the first time, during prenatal screening.

A mass spectrometry assay for detection of endogenous and lentiviral engineered hemoglobin in cultured cells and sickle cell disease mice

Sickle cell disease (SCD) results from a sequence defect in the β-globin chain of adult hemoglobin (HbA) leading to expression of sickle hemoglobin (HbS). It is traditionally diagnosed by cellulose-acetate hemoglobin electrophoresis or high-performance liquid chromatography. While clinically useful, these methods have both sensitivity and specificity limitations. We developed a novel mass spectrometry (MS) method for the rapid, sensitive and highly quantitative detection of endogenous human β-globin and sickle hβ-globin, as well as lentiviral-encoded therapeutic hβAS3-globin in cultured cells and small quantities of mouse peripheral blood. The MS methods were used to phenotype homozygous HbA (AA), heterozygous HbA-HbS (AS) and homozygous HbS (SS) Townes SCD mice and detect lentiviral vector-encoded hβAS3-globin in transduced mouse erythroid cell cultures and transduced human CD34+ cells after erythroid differentiation. hβAS3-globin was also detected in peripheral blood 6 weeks post-transplant of transduced Townes SS bone marrow cells into syngeneic Townes SS mice and persisted for over 20 weeks post-transplant. As several genome-editing and gene therapy approaches for severe hemoglobin disorders are currently in clinical trials, this MS method will be useful for patient assessment before treatment and during follow-up.

Hb Chapel Hill or Alpha2 74(EF3) Asp>Gly, a mildly unstable variant found in a Chinese family

BACKGROUND

Hb Chapel Hill [Alpha2 74(EF3) Asp > Gly] results from an GAC > GGC substitution at codon 74 of the HBA1 or HBA2 genes. Hb Chapel Hill has not been reported since 1986.

METHODS

A heterozygous mutation, HBA2: c.224A > G, was identified in the proband, her father and sister. We compared the haematological and clinical data of this family with the data reported in the limited number of individuals.

RESULTS

Having excluded iron deficiency, the Hb Chapel Hill was asymptomatic in heterozygous state. The cases presented here characterize cases in new techniques including capillary electrophoresis (CE). Two aberrant peaks were identified by CE, a major peak migrating in the zone 7 that correspond to Hb Chapel Hill (αChapel Hill 2β2) and a minor peak migrating in the zone 1 that correspond to Hb Chapel Hill2 (αChapel Hill 2δ2). Focusing on the variant expression, the Hb Chapel Hill plus Hb A2 variant were around 18.9-20.6% of total Hb in three members.

CONCLUSION

This data will be useful for providing up-to-date and high quality information on the Hb Chapel Hill.

Hb Q-Thailand heterozygosity unlinked with the (-α4.2/) α+-thalassemia deletion allele identified by long-read SMRT sequencing: hematological and molecular analyses

OBJECTIVE

In the present study, two unrelated cases of Hb Q-Thailand heterozygosity unlinked with the (-α^4.2/) α⁺-thalassemia deletion allele were identified by long-read single molecule real-time (SMRT) sequencing in southern China. The aim of this study was to report the hematological and molecular features as well as diagnostic aspects of the rare manifestation.

METHODS

Hematological parameters and hemoglobin analysis results were recorded. A suspension array system for routine thalassemia genetic analysis and long-read SMRT sequencing were applied in parallel for thalassemia genotyping. Traditional methods, including Sanger sequencing, multiplex gap-polymerase chain reaction (gap-PCR) and multiplex ligation-dependent probe amplification (MLPA), were used together to confirm the thalassemia variants.

RESULTS

Long-read SMRT sequencing was used to diagnose two Hb Q-Thailand heterozygous patients for whom the hemoglobin variant was unlinked to the (-α^4.2/) allele for the first time. The hitherto undescribed genotypes were verified by traditional methods. Hematological parameters were compared with those of Hb Q-Thailand heterozygosity linked with the (-α^4.2/) deletion allele in our study. For the positive control samples, long-read SMRT sequencing revealed a linkage relationship between the Hb Q-Thailand allele and the (-α^4.2/) deletion allele.

CONCLUSIONS

Identification of the two patients confirms that the linkage relationship between the Hb Q-Thailand allele and the (-α^4.2/) deletion allele is a common possibility but not a certainty. Remarkably, as it is superior to traditional methods, SMRT technology may eventually serve as a more comprehensive and precise method that holds promising prospects in clinical practice, especially for rare variants.

Molecular characterisation of Hb Akron [β52 (D3) Asp→Val] combined with thalassaemia in a Chinese family

AIMS

Hb Akron (HBB:c.158A>T) is a rare β-chain variant and many characteristics about its clinical features still remain unclear. In this study, we aimed to explore the molecular and haematological characterisations of previously undescribed states for Hb Akron associated with different forms of thalassaemia.

METHODS

Haematology and genetic analysis were performed in 9 members from a Chinese Zhuang ethnic family.

RESULTS

Hb Akron in various combinations with β0-thalassaemia and α0-thalassaemia were identified and characterised. Simple heterozygote for Hb Akron is asymptomatic, while the compound heterozygotes of Hb Akron associated with the β0-thalassaemia mutation generates a more severe haematological phenotype than Hb Akron or β0-thalassaemia mutation seen in isolation. The specific peak of Hb Akron appears at Zone D (195-225 s) in the state of heterozygote and compound heterozygote on haemoglobin capillary electrophoresis device, and the reduction of Hb Akron level in heterozygotes is proportional to the degree of α-globin gene deficiency.

CONCLUSIONS

We have for the first time described the genetic and haematological characteristics of Hb Akron combined with different thalassaemia mutations, which will provide useful information for genetic counselling and prenatal diagnostic service of this mutation in a population with high prevalence of thalassaemia.

The Spectrum of HBB Mutations among 2315 Beta Thalassemia Patients of a Reference Clinic in Tehran-Iran

Beta Thalassemia is the most prevalent and well-studied single gene disorder in Iran. Here, we investigated the spectrum of HBB gene mutations, identified among 2315 patients, referred to a reference thalassemia clinic in Tehran, on the basis of suspicion to thalassemia major or intermedia. The patients were homozygous or compound heterozygous for HBB mutations, and were referred from various Iranian provinces, during 15 years (2001- 2016). The HBB mutations were classified based on their frequency, and the result was compared to a meta-analysis of 14,293 beta thalassemia cases in the Iranian population, within the same time period. The mutation spectrum in this study contained 43 HBB mutations, compared to the 90, presented by the meta-analysis. Similar to the meta-analysis, IVSII-1 (G > A) and IVSI-5 (G > C) were the most common mutations in this study. These two comprised 62.40% of the total HBB mutant alleles in the studied population, comparable to 51.92% of that in the meta-analysis. IVSII-1 (G > A) and IVSI-5 (G > C), followed by 17 other mutations that had frequencies ranging from 0.15% to 5.44%, were among the 20 common HBB mutations in Iran and neighboring countries, according to the meta-analysis. This study provided further evidence to support the spectrum of the most common HBB mutations in the Iranian population.

Two Novel α-Thalassemia Mutations CD 39 -C [Thr > Pro] and CD 109 ACC > CCC [Thr > Pro] Identified in Two Chinese Families: A Case Report

We reported the identification of two rare α-thalassemia silent carriers with novel HBA1 mutations of CD 39 -C [Thr > Pro] (HBA1: c.114del; p.Thr39Profs*11) and CD 109 ACC > CCC [Thr > Pro] (HBA1: c.325A > C; p. Thr109Pro), respectively. The two probands were pregnant women diagnosed with mild hypochromic anemia or microcytic hypochromic anemia by routine blood tests. They started iron therapy before taking differential diagnosis from iron deficiency anemia. After wait and watch approach, they both accepted thalassemia genetic screening, which identified CD 39 -C [Thr > Pro] and CD 109 ACC > CCC [Thr > Pro], respectively. Due to inappropriate iron therapy, worse anemia and iron overload were noticed in the first proband, but no obvious side effect was found in both probands. Functional analysis showed that, relative to the wild type, CD 39 -C [Thr > Pro] considerably reduced the expression of the HBA1 protein while CD 109 ACC > CCC [Thr > Pro] only had a minor impact. Our study highlighted the importance of gestational thalassemia screening based on next-generation sequencing for identifying novel rare thalassemia variants and increased our understanding about the relationship between genotype and phenotype of α-thalassemia.

A Novel β-Globin Variant, Hb Raklev [β 75(E19) HBB:c.227T > A (Leu→Gln)]

We present a new hemoglobin variant, Hb Raklev, characterized by the substitution of leucine with glutamine at position 75 in the β-globin chain. This variant was discovered inadvertently during an HbA1c evaluation using high performance liquid chromatography in a symptomless 54-year-old Caucasian woman, with the same variant also identified in her 16-year-old daughter. Purification of the hemoglobin revealed possibly diminished 2,3-bisphosphoglycerate (2,3-BPG) sensitivity, which may result in heightened oxygen affinity. Notably, two variants have been previously documented at this location: the unstable Hb Atlanta and the high-affinity Hb Pasadena.

Mutation Spectrum of β-Globin Gene in Patients with β-Thalassemia at Tidar Hospital, Magelang, Central Java, Indonesia

β-Thalassemia is genetic disorder characterized by β-globin chain deficiency resulting from mutations in the β-globin coding gene. Both the quantity and quality of blood produced will be impacted by this condition. The distribution of mutation causing thalassemia is vary across ethnic and different regions in Indonesia. This study aims to identify the variant mutation in patients with β-thalassemia at Tidar Hospital as representative samples of Javanese population, the largest ethnicity in Indonesia. Sixty-one blood samples were obtained from blood transfusion-dependent patients with β-thalassemia. Mutation was identified using ARMS and RFLP PCR-based methods, and inconclusive samples were subjected to DNA sequencing. Results showed that the mutation variants were Cd 26/IVSI-5 (G > C) 47.54%, Cd 26/Cd 35 16.30%, Cd 26/IVSI-1 (G > T) 11.47%, Cd 26/IVSI-2 4.91%, IVSI-5 (G > C)/Cd 40 3.27%; 1.63%; IVSI-5 (G > C)/IVSI-1 (G > A) 1.63%; IVSI-5 (G > C)/Cap + 1 1.63%; Cd 26/Cd 15 1.63%; Cd 26/Cd 30 1.63%. We also found three homozygous of IVSI-1 (G > T), IVSI-5 (G > C) 6.55%, and Cd 35 1.63%. The most prevalent alleles would be recommended to be used as part of screening for β-thalassemia in the Javanese ethnicity in Central Java, especially for families affected by thalassemia.

Hemoglobin β-Globin Variants In Hispanic Patients: An Institutional Experience From Dallas, Texas

Hemoglobinopathies are the most common single-gene disorders in humans. There are 1,424 variants of human hemoglobin described with 951 involving the β-globin gene. Ancestry and geography play a significant role in the incidence and nature of hemoglobinopathies, with African, Asian, and Mediterranean populations and their descendants being amongst the most affected. Investigation of variants in individuals of Hispanic descent is needed to reflect the changing demographics of the United States. Hemoglobin β-globin evaluation through gel electrophoresis, high-performance liquid chromatography, and HBB gene sequencing was performed on patients from Texas hospitals between 2010 and 2015 and demographic parameters (age, sex, ethnicity) was subsequently analyzed. A total of 846 patients underwent hemoglobinopathy evaluation. A β chain variant was detected in 628 of the 846 total patients. Hispanic patients represented 37% (314/846 patients), which were equally distributed between females (50%; 156/314) and males (50%; 156/314). A β-globin chain variant was found in 67% of Hispanic patients with a distribution across 10 variants seen in greater than 1% of patients. For hemoglobin variants, an understanding of the regional and ethnic prevalence will improve patient care through more effective screening and identification of the variant, early diagnosis, and appropriate treatment if necessary, and better genetic counseling.

Molecular analysis and clinical significance of hemoglobin Quong Sze in Huizhou city, Southern China

OBJECTIVE

Hemoglobin Quong Sze (Hb QS) is one of the most common non-deletional α-thalassemia (α-thal), which is prevalent in the Southern Chinese population. However, there are still few comprehensive researches on the molecular characterization of Hb QS. So it is important to find out appropriate diagnosis and characterization of Hb QS carrier for genetic counseling.

MATERIALS AND METHODS

A hematological screening including hematological indices and hemoglobin analysis was performed in 113,400 individuals from Huizhou city, Southern China. Then, suspected thalassemia carriers were detected by a suspension-array system and DNA sequencing for α- and β-thal.

RESULTS

In our study, we identified 521 subjects who were Hb QS carriers, including fourteen different genotypes. Among them, 445 Hb QS heterozygotes showed a decrease in the mean corpuscular hemoglobin (MCH), 16 compound heterozygotes for Hb QS/α+-thal presented mild thalassemia, 28 Hb QS in combination with --SEA/αα manifested as Hb H disease, varying clinical symptoms from only moderate anemia to severe anemia and requiring blood transfusion, and 29 double heterozygotes for Hb QS and β-thal behaved as β-thal trait. The mean corpuscular volume (MCV) and MCH were significantly reduced and no Hb H peak could be detected in one patient with Hb H-Hb QS and β-thal. Meanwhile, we identified two homozygous Hb QS carriers, who showed mild to moderate anemia and increased Hb A2 level but negative results from a sequencing analysis for the first time. Additionally, Comparison of hematological parameters among the major four genotype groups showed significant differences in most box-whisker plots.

CONCLUSION

People who originated from Huizhou city showed many genotypes and diversity in the clinical manifestations of Hb QS carriers. This study enlarges the mutation spectrum of α-thal and emphasizes that reliable detection of the gene mutations is important for genetic counseling. It also strengthens the prevention and control of thalassemia.

The beta thalassaemia trait in Jamaica

The objective of this study was to review the prevalence and features of the beta thalassaemia trait in Jamaican populations. Screening of 221,306 newborns over the last 46 years has given an indication of the distribution and prevalence of beta thalassaemia genes, and screening of 16,612 senior school students in Manchester parish, central Jamaica, has provided their haematological features. The prevalence of the beta thalassaemia trait predicted from double heterozygotes was 0.8% of 100,000 babies in Kingston, 0.9% of 121,306 newborns in southwest Jamaica, and 0.9% of school students in Manchester. Mild beta+ thalassaemia variants (-88 C>T, -29 A>G, -90 C>T, polyA T>C) accounted for 75% of Kingston newborns, 76% of newborns in southwest Jamaica, and 89% of Manchester students. Severe beta+ thalassaemia variants were uncommon. Betao thalassaemia variants occurred in 43 patients and resulted from 11 different variants of which the IVSII-849 A>G accounted for 25 (58%) subjects. Red cell indices in IVSII-781 C>G did not differ significantly from HbAA, and this is probably a harmless polymorphism rather than a form of beta+ thalassaemia; the removal of 6 cases in school screening had a minimal effect on the frequency of the beta thalassaemia trait. Red cell indices in the beta+ and betao thalassaemia traits followed established patterns, although both were associated with increased HbF levels. The benign nature of beta+ thalassaemia genes in Jamaica means that cases of sickle cell-beta+ thalassaemia are likely to be overlooked, and important clinical questions such as the role of pneumococcal prophylaxis remain to be answered.

The pivotal role of HbA1c assay to detect hemoglobinopathies: A 5-year observational retrospective study in the population of Southern France

Background and Aims

Mobility and migration flows are growing from different countries of the world to European countries, including France and in particular the Mediterranean basin. This study aimed to investigate the presence of hemoglobin (Hb) variants in outpatients/inpatients of the Montpellier Hospital (France) in whom an HbA1c assay had been performed and for which the country of birth had been informed.

Methods

This is a retrospective study from January 2016 to December 2020 based on all high-performance liquid chromatography (HPLC) chromatograms (Tosoh Bioscience HLC-723G8) having an alarm of suspected Hb variant during HbA1c measurement. The corresponding samples were systematically sent to the hematology laboratory for confirmation and identification of Hb variant. Patient's medical history, clinical and demographic data were extracted from each medical chart. Statistical analyses were performed using XLSTAT® software, version 2016.06.35661.

Results

Three hundred sixty-three patients were confirmed with Hb variant exhibiting 17 different Hb profiles, highlighting the pivotal role of glycated hemoglobin (HbA1c) as a detection step. The prevalence of Hb variant in this southern French population was 0.71%, with the highest frequency for the beta-globin variants (n = 342/363; i.e., 94.2%), including the most common: S, C, E, and D in 200/342 (58.5%), 83/342 (24.3%), 29/342 (8.5%), and 11/342 (3.2%), respectively. Among patients with Hb variants, almost half (165/363; i.e., 45.4%) were born in the African continent with a predominance for Morocco (32/165; i.e., 19.3%) and Algeria (29/165; i.e., 17.5%).

Conclusion

HbA1c assay is a useful tool to detect Hb variants. Hemoglobinopathies are a public health issue in the current French population which is a multiethnic society. Despite the monocentric nature of our study, we note a high frequency of Hb variants in the south of France, which underlines the importance of screening for Hb variants in the whole population.

Case report: Curing a rare, unstable hemoglobin variant Hb Bristol-Alesha using haploidentical hematopoietic stem cell transplantation

Unstable hemoglobinopathies are a rare, heterogeneous group of diseases that disrupt the stability of hemoglobin (Hb), leading to chronic hemolysis and anemia. Patients with severe phenotypes often require regular blood transfusions and iron chelation therapy. Although rare, studies have reported that hematopoietic stem cell transplantation (HSCT) seems to be an available curative approach in transfusion-dependent patients with unstable hemoglobinopathies. Here, we describe successful haploidentical HSCT for the treatment of an unstable Hb variant, Hb Bristol-Alesha, in a 6-year-old boy with severe anemia since early childhood. Two years after transplantation, he had a nearly normal hemoglobin level without evidence of hemolysis. DNA analysis showed complete chimerism of the donor cell origin, confirming full engraftment with normal erythropoiesis.

Detection of a Rare Mutation in the Initiation Codon of the β-Globin Gene (HBB:C.2T > C; P.Met1Thr)

β-thalassemia is one of the most common inherited autosomal disorders in the northern Iraqi Kurdistan region. This study reports a rare mutation in the initiation codon of the β-globin gene (HBB: c.2T > C; p.Met1Thr) in an 11-year-old male with severe transfusion-dependent β-thalassemia. Molecular testing to uncover the mutations of the β-globin gene in the proband and his parents was performed by amplification and reverse hybridization. Sanger sequencing was conducted for further identification. A severe β-globin gene mutation in codon 8/9 [+G] was initially identified in the proband and his mother's DNA samples. However, the detection of only one β-globin gene mutation was not enough to elucidate the patient's severe phenotype. Thus, a rare mutation in the initiation codon was identified later in the proband and his father by Sanger sequencing. In thalassemias, the presence of a rare mutation should be suspected when the patient's genotype does not correlate with the phenotype.

[Hemoglobin C Variant Affecting Glycated Hemoglobin Test Results: A Rare Case Report]

Hemoglobin (Hb) variants are common factors that affect the results of glycosylated hemoglobin (A1C) tests. Hemoglobin variants react differently to different testing methods. Herein, we presented the first ever report of the effect of hemoglobin C (Hb C) on the test results of A1C in the Chinese population. High performance liquid chromatography (HPLC) and capillary electrophoresis were performed to measure A1C. Hemoglobin electrophoresis was conducted to identify the hemoglobin variants. Hb sequencing was performed to determine the mutation sites on the β chain. HPLC showed decreased A1C results, which could be corrected by electrophoresis, but the electrophoresis graph still showed abnormal peaks. The hemoglobin electrophoresis results suggested that there were hemoglobin variants, which hemoglobin sequencing results revealed to be Hb C. Uncommon variations in a specific population tend to be overlooked. To avoid clinical decision-making being affected by the results of a single test, we recommend that an explanatory reporting model be routinely adopted for A1C tests so that all reports always contain explanatory notes for the testing methodology and analysis of the graphs.

The diagnosis and molecular analysis of a novel 27.2 kb deletion causing α0-thalassemia

BACKGROUND

Thalassemia, one of the most prevalent monogenic diseases worldwide, is caused by an imbalance of α-like and non-α-like globin chain production. Copy number variations, which cause the most common genotype of α-thalassemia, can be detected by multiple diagnostic methods.

CASE REPORT

The proband was a 31-year-old female who was diagnosed with microcytic hypochromic anemia by antenatal screening. Hematological analysis and molecular genotyping were conducted on the proband and the proband's family members. Gap-polymerase chain reaction, Sanger sequencing, multiplex ligation-dependent probe amplification, and next-generation sequencing were used to detect potentially pathogenic genes. Familial studies and genetic analyses revealed a novel deletion of 27.2 kb located in the α-globin gene cluster (NC_000016.9: g. 204538_231777delinsTAACA).

CONCLUSIONS

We reported a novel α-thalassemia deletion and described the process of molecular diagnosis. The novel deletion extends the thalassemia mutation spectrum, which may be helpful in genetic counseling and clinical diagnosis in the future.

Next-Generation Sequencing (NGS) and Third-Generation Sequencing (TGS) for the Diagnosis of Thalassemia

Thalassemia is one of the most heterogeneous diseases, with more than a thousand mutation types recorded worldwide. Molecular diagnosis of thalassemia by conventional PCR-based DNA analysis is time- and resource-consuming owing to the phenotype variability, disease complexity, and molecular diagnostic test limitations. Moreover, genetic counseling must be backed-up by an extensive diagnosis of the thalassemia-causing phenotype and the possible genetic modifiers. Data coming from advanced molecular techniques such as targeted sequencing by next-generation sequencing (NGS) and third-generation sequencing (TGS) are more appropriate and valuable for DNA analysis of thalassemia. While NGS is superior at variant calling to TGS thanks to its lower error rates, the longer reads nature of the TGS permits haplotype-phasing that is superior for variant discovery on the homologous genes and CNV calling. The emergence of many cutting-edge machine learning-based bioinformatics tools has improved the accuracy of variant and CNV calling. Constant improvement of these sequencing and bioinformatics will enable precise thalassemia detections, especially for the CNV and the homologous HBA and HBG genes. In conclusion, laboratory transiting from conventional DNA analysis to NGS or TGS and following the guidelines towards a single assay will contribute to a better diagnostics approach of thalassemia.

Compact zinc finger base editors that edit mitochondrial or nuclear DNA in vitro and in vivo

DddA-derived cytosine base editors (DdCBEs) use programmable DNA-binding TALE repeat arrays, rather than CRISPR proteins, a split double-stranded DNA cytidine deaminase (DddA), and a uracil glycosylase inhibitor to mediate C•G-to-T•A editing in nuclear and organelle DNA. Here we report the development of zinc finger DdCBEs (ZF-DdCBEs) and the improvement of their editing performance through engineering their architectures, defining improved ZF scaffolds, and installing DddA activity-enhancing mutations. We engineer variants with improved DNA specificity by integrating four strategies to reduce off-target editing. We use optimized ZF-DdCBEs to install or correct disease-associated mutations in mitochondria and in the nucleus. Leveraging their small size, we use a single AAV9 to deliver into heart, liver, and skeletal muscle in post-natal mice ZF-DdCBEs that efficiently install disease-associated mutations. While off-target editing of ZF-DdCBEs is likely too high for therapeutic applications, these findings demonstrate a compact, all-protein base editing research tool for precise editing of organelle or nuclear DNA without double-strand DNA breaks.

A Case of Misdiagnosis Caused by the Coinheritance of Hb G-Siriraj [β7(A4)Glu→Lys; HBB: c.22G>A] and Hb H Disease

Despite the fact that most hemoglobin (Hb) variants are clinically and hematologically silent, they can interact with thalassemias, which could sometimes give rise to complicated routine thalassemia diagnostics. Hb G-Siriraj [β7(A4)Glu→Lys; HBB: c.22G>A] alone is a benign condition, but its coinheritance with α-thalassemia (α-thal) may lead to misdiagnosis. We describe the case of a Chinese woman with an elevated Hb A₂ level who was assumed to carry heterozygous β-thalassemia (β-thal), but was later shown to be a double heterozygote for Hb G-Siriraj and Hb H disease. This study for the first time described hematological characteristics of a patient with a double heterozygosity for Hb G-Siriraj and Hb H disease. It is of great significance for technicians and clinicians to expand their knowledge as well as to help guide clinical diagnosis, population screening and genetic counseling.

Hb Huadu [α124(H7)Ser→Thr (TCC>ACC), HBA2: c.373T>A]: A Novel Variant of the α-Globin Gene

Here, we report a novel α chain hemoglobin (Hb) variant found during routine thalassemia screening. This Hb variant can be detected by capillary electrophoresis (CE) but cannot be recognized by high performance liquid chromatography (HPLC). Sanger sequencing revealed a heterozygous missense substitution at nucleotide 373 on the HBA2 gene, which results in the replacement of serine by threonine at codon 124 [α124(H7)Ser→Thr (TCC>ACC), HBA2: c.373T>A]. It is the first report of this variant, named Hb Huadu for the birthplace of the proband. In addition, the proband coinherited the heterozygous codons 41/42 (-TTCT) (HBB: c126_129delCTTT) on the β-globin gene.

Effect of deletions in the α-globin gene on the phenotype severity of β-thalassemia

Thalassemia is the most common inherited hemoglobinopathy worldwide. Variation of clinical symptoms in this hemoglobinopathy entails differences in disease-onset and transfusion requirements. The aim of this study was to investigate the role of α-globin gene deletions in modulating the clinical heterogeneity of β-thalassemia (β-thal) syndromes. A total number 270 β-thal subjects were enrolled. Hematological parameters were recorded. β-Globin mutations were determined by amplified refractory mutation system-polymerase chain reaction (ARMS-PCR), gap-PCR and Sanger sequencing. α-Globin gene deletions were determined by multiplex PCR. Out of 270 β-thal subjects, 19 carried β⁺/β⁺, 74 had β⁰/β⁰ and 177 had the β⁰/β⁺ genotype. When we determined the severity of the different β-thal subjects in coinherited with the α gene deletion, it was revealed that, 84.2% β⁺/β⁺ subjects carried a non severe phenotype and did not have an α gene deletion. Of the β⁰/β⁰ individuals, 95.9% presented a severe phenotype, irrespective of α-globin gene deletions. In cases with the β⁰/β⁺ genotype, 19.2% subjects also carried a deletion on the α gene. Of these, 61.8% presented a non severe phenotype and 38.2% were severely affected. Only in the β⁰/β⁺ category did α gene deletions make a significant contribution (p < 0.001) toward alleviation of clinical severity. Therefore, it can be stated that α-globin gene deletions play a role in ameliorating the phenotype in patients with a β⁺/β⁰ genotype.

β-Thalassemia Intermedia Caused by the β-Globin Gene 3' Untranslated Region: Another Case Report

The 3' untranslated region (3'UTR) is associated with mRNA stability because of its involvement in 3' end processing, polyadenylation, and mRNA capping. Mutations located in this area can cause a phenotype compatible with β⁺-thalassemia (β⁺-thal). We report a Chinese subject with β-thal intermedia (β-TI) who developed transfusion-dependent anemia. Molecular studies revealed that the patient was a compound heterozygote for two β-thal alleles: codons 41/42 (-TTCT) (HBB: c.126_129delCTTT) and term codon +32 (A>C) (HBB: c.*32A>C).

Thalassaemia

Thalassaemia is a diverse group of genetic disorders with a worldwide distribution affecting globin chain synthesis. The pathogenesis of thalassaemia lies in the unbalanced globin chain production, leading to ineffective erythropoiesis, increased haemolysis, and deranged iron homoeostasis. The clinical phenotype shows heterogeneity, ranging from close to normal without complications to severe requiring lifelong transfusion support. Conservative treatment with transfusion and iron chelation has transformed the natural history of thalassaemia major into a chronic disease with a prolonged life expectancy, albeit with co-morbidities and substantial disease burden. Curative therapy with allogeneic haematopoietic stem cell transplantation is advocated for suitable patients. The understanding of the pathogenesis of the disease is guiding therapeutic advances. Novel agents have shown efficacy in improving anaemia and transfusion burden, and initial results from gene therapy approaches are promising. Despite scientific developments, worldwide inequality in the access of health resources is a major concern, because most patients live in underserved areas.

High-Throughput Variant Detection Using a Color-Mixing Strategy

Many diseases are related to multiple genetic alterations along a single gene. Probing for highly multiple (>10) variants in a single quantitative PCR tube is not possible because of a limited number of fluorescence channels and one variant per channel, so many more tubes are needed. Herein, a novel color-mixing strategy that uses fluorescence combinations as digital color codes to probe multiple variants simultaneously was experimentally validated. The color-mixing strategy relies on a simple intratube assay that can probe for 15 variants as part of an intertube assay that can probe for an exponentially increased number of variants. This strategy is achieved by using multiplex double-stranded toehold probes modified with fluorophores and quenchers; the probes are designed to be quenched or luminous after binding to wild-type or variant templates. The color-mixing strategy was used to probe for 21 pathogenic variants in thalassemia and to distinguish between heterozygous and homozygous variants in six tubes, with a specificity of 99% and a sensitivity of 94%. To support tuberculosis diagnosis, the same strategy was applied to simultaneously probe in Mycobacterium tuberculosis for rifampicin-resistance mutations occurring within one 81-bp region and one 48-bp region in the rpoB gene, plus five isoniazid-resistance mutations in the inhA and katG genes.

Spectrum of β-Thalassemia Mutations in Some Areas of Guangxi Zhuang Autonomous Region of Southern China: A Study on a Pediatric Population Aged 0-15 Years

β-Thalassemia (β-thal), one of the most common form of single-gene inheritable blood diseases in the world, is highly prevalent in southern China, especially in the Guangxi Zhuang Autonomous Region. To update the β-thal mutation spectrum in this region, we performed hematological and genetic analyses on 888 β-thal major (β-TM), β-thal intermedia (β-TI) and β-thal carrier patients, aged 0-15 years old, from different parts of Guangxi Province. We identified 55 genotypes and 18 β-thal mutations. The codons 41/42 (-TTCT) (HBB: c.126_129delCTTT) (43.97%), codon 17 (A>T) (HBB: c.52A>T) (25.43%), -28(A>G) (HBB: c.-78A>G) (8.18%), IVS-II-654 (C>T) (HBB: c.316-197C>T) (7.85%) and codon 26 (G>A) (HBB: c.79G>A) (5.02%) were the five most common, accounting for more than 90.0%. The results of our study are providing an up-to-date β-thal mutation spectrum in the 0-15-year-old pediatric population, which will help genetic counseling and prevention of β-TM in mainland China's most endemic region, Guangxi Zhuang Autonomous Region.

A Novel Hemoglobin Variant Hb Liaobu [α107(G14)Val→Leu, HBA2: c.322G>C] Detected by Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry

We here describe a novel hemoglobin (Hb) variant, Hb Liaobu [α107(G14)Val→Leu, HBA2: c.322G>C], in a Chinese family. The structurally abnormal α chain variant could not be detected using capillary electrophoresis (CE) and was subsequently characterized by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry (MS), and further confirmed by reversed phase high performance liquid chromatography (HPLC). Sanger sequencing revealed a novel base mutation on the α2-globin gene and RNA analysis by reverse transcription polymerase chain reaction (RT-PCR) showed the presence of an abnormal HBA transcript. The isopropanol stability test indicated the stable state of this structural Hb variant. In conclusion, a new Hb variant, Hb Liaobu, was discovered and characterized. It was proven to be a nonpathogenic variant. Our study resolved the confusion in the clinical diagnosis of individuals with this novel Hb variant in this family.

The first Chinese case of unstable Hemoglobin Santa Ana detected by capillary electrophoresis: a case report and literature review

Hemoglobin Santa Ana [β88(F4)Leu→Pro (CTG > CCG) HBB: c.266T > C] is an unstable hemoglobin variant characterized by a substitution of the amino acid leucine by proline at the 88th position of the β-globin chain. We for the first time identified this hemoglobin variant in a Chinese patient by capillary electrophoresis (CE). The proband was an 8-year-old boy with chronic anemia, brown urine and splenomegaly. He had been affected by moderate anemia, twice approaching a severe degree, that was attributed to infection. The CE result revealed an abnormal hemoglobin peak at electrophoretic zone 4 that correspond to the hemoglobin Santa Ana peak, and a CTG > CCG mutation at codon 88 of the β-globin gene was confirmed by DNA sequencing. To avoid misdiagnosis and genetic risks, a literature review of other unstable hemoglobins that migrate similarly to the hemoglobin Santa Ana was performed. Our findings indicate that hemoglobin Santa Ana can be clearly separated by CE, with accurate diagnosis depending on molecular analysis. This information will be useful for providing appropriate genetic counselling and for prenatal diagnosis.

An Evaluation for the Causes of Reduced Hb A2 and the Molecular Characterization of HBD Variants in Hong Kong

Prenatal screening of β-thalassemia (β-thal) carriers is based on the hallmark phenotype of microcytosis and raised Hb A₂. The unanticipated birth of β-thal major (β-TM) offspring to β-thal carriers who were misdiagnosed during prenatal screening have been reported. A subset of these resulted from the masked phenotype due to the coinheritance of HBD variants. In a broader sense, the causes of reduced Hb A₂ in thalassemia screening, the prevalence and spectrum of HBD variants in Hong Kong remain to be characterized. Over a 13-month period, a total of 2982 samples were referred for thalassemia screening. Surplus samples with reduced Hb A₂ levels (2.0%) were evaluated. HBD variations were assessed by direct sequencing. Sixty-six samples were tested. Hb H disease, HBD variants, α-thalassemia (α-thal) trait and iron deficiency were detected in 40 (60.6%), 12 (18.2%), eight (12.1%) and seven (10.6%) samples, respectively. Seven samples carried more than one of the mentioned conditions. The cause remained elusive in seven samples. Thirteen HBD variants were detected and two were recurrent, including HBD: c.-127T>C [-77 (T>C)] and HBD: c.314G>A (Hb Chori-Burnaby). A novel nonsense variant HBD: c.262C>T [codon 87 (C>T)] was detected in cis with HBD: c.-127T>C. Overall, the prevalence of HBD variants was 0.4%. This study advanced our understanding of the causes of reduced Hb A₂ in clinical practice and identified hereditary disorders of α- and δ-globin genes as the prevailing causes. It established the landscape of HBD variations in our locality and highlighted the pitfall of phenotypic screening of β-thal carriers.

A novel 4.9 Kb deletion at beta-globin gene is identified by the third-generation sequencing: case report from Baoan, China

BACKGROUND

Thalassemia is a common inherited haemoglobin disorder worldwide, several methods have been utilized in the step-wise screening. Even though hundreds of mutations in globin genes have been reported, novel mutations are continuously emerging as the development of DNA sequencing.

METHODS

The case is a 27-year-old female with abnormal values of routine hematological indices, who was admitted for genetic screening of thalassemia. Genomic DNA was extracted and used for genetic assays cover 26 mutations in HBA and HBB genes: gap-PCR and agarose gel electrophoresis were performed to detect deletions, while PCR-reverse dot blot was used to detect point mutations. The next- and third- generation sequencing were used to identify the known and potential novel genotypes of thalassemia, and multiplex ligation-dependent probe amplification (MLPA) was used for genotype validation.

RESULTS

Hematological results indicate microcytic hypochromic anemia, high HbA2 (7.2%) and high HbF (6.2%). None of the known genotypes of thalassemia were matched for this case, but a novel 4.9 Kb deletion at HBB gene (hg38, Chr11: 5226187-5231089) was discovered by the third-generation sequencing, the novel deletion was also validated by MLPA (8 probes, 11p15.4: 203314-207652).

CONCLUSIONS

This study suggests the third-generation sequencing has promising potentiality to discover novel genotypes (especially deletions) of thalassemia.

Innate Variability in Physiological and Omics Aspects of the Beta Thalassemia Trait-Specific Donor Variation Effects

The broad spectrum of beta-thalassemia (βThal) mutations may result in mild reduction (β ⁺⁺), severe reduction (β ⁺) or complete absence (β ⁰) of beta-globin synthesis. βThal heterozygotes eligible for blood donation are "good storers" in terms of red blood cell (RBC) fragility, proteostasis and redox parameters of storage lesion. However, it has not been examined if heterogeneity in genetic backgrounds among βThal-trait donors affects their RBC storability profile. For this purpose, a paired analysis of physiological and omics parameters was performed in freshly drawn blood and CPD/SAGM-stored RBCs donated by eligible volunteers of β ⁺⁺ (N = 4), β ⁺ (N = 9) and β ⁰ (N = 2) mutation-based phenotypes. Compared to β ⁺, β ⁺⁺ RBCs were characterized by significantly lower RDW and HbA₂ but higher hematocrit, MCV and NADPH levels in vivo. Moreover, they had lower levels of reactive oxygen species and markers of oxidative stress, already from baseline. Interestingly, their lower myosin and arginase membrane levels were accompanied by increased cellular fragility and arginine values. Proteostasis markers (proteasomal activity and/or chaperoning-protein membrane-binding) seem to be also diminished in β ⁺⁺ as opposed to the other two phenotypic groups. Overall, despite the low number of samples in the sub-cohorts, it seems that the second level of genetic variability among the group of βThal-trait donors is reflected not only in the physiological features of RBCs in vivo, but almost equally in their storability profiles. Mutations that only slightly affect the globin chain equilibrium direct RBCs towards phenotypes closer to the average control, at least in terms of fragility indices and proteostatic dynamics.

First Report of the 3'-Untranslated Region +1506 (A>C) [NM_000518.5: c.*32A>C] mutation on the β-Globin Gene in the Indian Population

The 3'-untranslated region (3'-UTR) is well known to be associated with the post-transcriptional regulation, because of the presence of important sequences that influence the fate of mRNA, and thus, in protein synthesis. The present study describes a point mutation on the β-globin 3'-UTR, +1506 (A>C) (HBB: c.*32A>C) in an Indian family during prenatal diagnosis (PND) screening of an at-risk couple. The members of the family heterozygous for this mutation presented with a typical β-thalassemia (β-thal) phenotype. The haplotype analysis of the β-globin gene cluster was determined for this mutation and observed to be linked with haplotype [- + - + + + +]. Common α-globin gene deletions, triplication, and the Xmnl polymorphism, were also looked for and found to be absent in the family. The identified HBB: c.*32A>C mutation is located in the first adenylate uridylate (AU) motif of the four AU motifs situated in the 3'-UTR region of the β-globin gene. Bioinformatics analysis revealed binding of two miRNAs, hsa-miR-451a and hsa-miR-3914, at the mutation position, possibly influencing the mRNA stability by recruiting RNA binding proteins. This is the third publication reporting the 3'-UTR +1506 (A>C) mutation worldwide and the first report of the existence of this mutation in the Indian population, emphasizing the high heterogeneity of this population.

Updated Molecular Spectrum of β-Thalassemia Mutations in Duhok Province, Northern Iraq: Ethnic Variation and the Impact of Immigration

Immigration impact on genetic epidemiology of thalassemia worldwide is well-recognized. Over the past decade, the Duhok Province of Northern Iraq attracted a large number of immigrants. To assess whether immigration had contributed to changes in the mutation spectrum of β-thalassemia (β-thal) in the region, we recruited 218 registered patients with symptomatic β-thal. The recruited patients included 50 (22.9%) from resettled migrant families. A total of 431 β-thal alleles were fully characterized, with 20 different thalassemia mutations, the most frequent being IVS-II-1 (G>A) (HBB: c.315 + 1G>A), IVS-I-6 (T>C) (HBB: c.92 + 6T>C), codon 5 (-CT) (HBB: c.17_18delCT), IVS-I-110 (G>A) (HBB: c.93-21G>A), codon 44 (-C) (HBB: c.135delC), codon 8 (-AA) (HBB: c.25_26delAA) and IVS-I-1 (G>A) (HBB: c.92 + 1G>A) constituting 72.8% of the total. Some differences in mutation spectrum were observed compared to earlier studies from this same province, the most notable of which were the higher frequencies of IVS-I-110 and codon 8. Interestingly, the highest proportions of alleles related to immigrants were encountered in these two allele groups. Ethnic variation was also documented, so that while Muslim Kurds had IVS-II-1, IVS-I-6, IVS-I-110, codon 5 and codon 44 as their most frequent mutations, the most frequent among Kurdish Yazidis, were codon 5, codon 44, codon 8 and IVS-I-6. These ethnic variations and changes in mutation spectrums are important and should be taken in consideration to ensure effective implementation of the thalassemia preventive program.

Cyanosis, hemolysis, decreased HbA1c and abnormal co-oximetry in a patient with hemoglobin M Saskatoon [HBB:c.190C > T p.His64Tyr]

We describe a first Dutch case of Hb M Saskatoon (HBB:c.190C > T p.His64Tyr) in a 47-year-old female Dutch patient who presented with cyanosis, hemolysis, and abnormal co-oximetry. A mean corpuscular volume (MCV) of 105 fL caused by reticulocytosis (160 × 10⁹/L) and low red blood cell count (3.6 × 10¹²/L) suggested an increased erythrocyte turnover. An HPLC glyco-globin analysis revealed a decreased HbA1c fraction of 12.3 mmol/mmol, HbA0 of 93.3% and an additional unidentified fraction at 1.2 min. DNA sequencing revealed a missense mutation in the HBB gene, (HBB:c.190C > T p.His64Tyr), known as Hb M Saskatoon, a variant which has been previously identified as an unstable hemoglobin variant leading to methemoglobinemia and anemia. In this report, we describe the clinical and remarkable laboratory aspects of our patient with Hb M Saskatoon, and the consequences for treatment and drug use.

Primary HBB gene mutation severity and long-term outcomes in a global cohort of β-thalassaemia

In β-thalassaemia, the severity of inherited β-globin gene mutations determines the severity of the clinical phenotype at presentation and subsequent transfusion requirements. However, data on associated long-term outcomes remain limited. We analysed data from 2109 β-thalassaemia patients with available genotypes in a global database. Genotype severity was grouped as β⁰ /β⁰ , β⁰ /β⁺ , β⁺ /β⁺ , β⁰ /β⁺⁺ , β⁺ /β⁺⁺ , and β⁺⁺ /β⁺⁺ . Patients were followed from birth until death or loss to follow-up. The median follow-up time was 34·1 years. Mortality and multiple morbidity outcomes were analyzed through five different stratification models of genotype severity groups. Interestingly, β⁰ and β⁺ mutations showed similar risk profiles. Upon adjustment for demographics and receipt of conventional therapy, patients with β⁰ /β⁰ , β⁰ /β⁺ , or β⁺ /β⁺ had a 2·104-increased risk of death [95% confidence interval (CI): 1·176-3·763, P = 0·011] and 2·956-increased odds of multiple morbidity (95% CI: 2·310-3·784, P < 0·001) compared to patients in lower genotype severity groups. Cumulative survival estimates by age 65 years were 36·8% for this subgroup compared with 90·2% for patients in lower genotype severity groups (P < 0·001). Our study identified mortality and morbidity risk estimates across various genotype severity groups in patients with β-thalassaemia and suggests inclusion of both β⁺ and β⁰ mutations in strata of greatest severity.

Strategies to improve pharmacogenomic-guided treatment options for patients with β-hemoglobinopathies

Drug efficacy and toxicity are closely related to the unique genetic profile of individuals, or pharmacogenomics. Despite the fact that cardiology, psychiatry and oncology are among the clinical specialties in which pharmacogenomics has become a clinical reality, the utility of pharmacogenomics has yet to be demonstrated for several other medical specialties. Over the last 15 years, genomic variants in a number of loci have been shown to be significantly associated with the fetal hemoglobin (HbF) response to hydroxyurea, the only approved drug for HbF induction for sickle cell disease. Here, we provide an update and discuss future challenges to the application of pharmacogenomics to improve therapies for β-hemoglobinopathies in relation to the current pharmacological treatment modalities for those disorders.

IVS-II-16 (G>C) (HBB: c.315+16G>C) or IVS-II-666 (C>T) (HBB: c.316-185C>T) Mutations Trigger an Hb S (HBB: c.20A>T)/β+-Thalassemia Phenotype in an Hb S Trait Patient

Sickle cell trait is a medical condition caused by the presence of both mutant Hb S (HBB: c.20A>T) and normal Hb A alleles. Although sickle cell trait is typically considered to be asymptomatic and benign, genetic modifiers and mutations can lead to severe clinical complications. In this study, the possible pathogenicity of the IVS-II-16 (G>C) (HBB: c.315+16G>C) and IVS-II-666 (C>T) (HBB: c.316-185C>T) mutations, which are considered to be neutral polymorphisms, and the association between the Hb S mutation are presented. To the best of our knowledge, these polymorphisms have not been previously reported in any sickle cell trait patient, and no relevant studies have been conducted. We recently studied a 40-year-old woman (proband), diagnosed to be an Hb S/β-thalassemia (β-thal) carrier. β-Globin mutations were analyzed using a DNA sequencer based on the Sanger method. The HbVar and ClinVar databases show IVS-II-16 and IVS-II-666 to be intronic mutations. However, statements in these data banks contradict our findings. In the present study, a transfusion-dependent Hb S patient, behaving as an Hb S/β-thal case due to these mutations, was reported. These mutations have not been previously reported in an Hb S patient. Although the IVS-II-16 and IVS-II-666 mutations were previously reported as benign, they converted the Hb S phenotype to transfusion-dependent Hb S/β-thal when combined with Hb S. In this regard, IVS-II-16 and IVS-II-666 mutations may not be innocent, as previously thought.