IthaGenes: an interactive database for haemoglobin variations and epidemiology

First Report of a Coincidental Discovery of Hb Antibes-Juan-Les-Pins (HBB: c.349_350insGTGTGCTGGCCC) in a Greek Woman

The rare Hb Antibes-Juan-Les-Pins (HBB: c.349_350insGTGTGCTGGCCC) was first reported in France. Hb Antibes-Juan-Les-Pins seems to be an innocuous variant and few published data are available. Heterozygous carriers have mild clinical or hematological findings. The abnormal hemoglobin (Hb) is detected by high performance liquid chromatography (HPLC) or capillary zone electrophoresis (CZE), but confirmation of the variant requires molecular analysis. This is the first description of Hb Antibes-Juan-Les-Pins heterozygosity in a woman of Greek origin.

A study of red blood cell alloimmunization and autoimmunization among 200 multitransfused Egyptian β thalassemia patients

The development of hemolytic erythrocyte alloantibodies and autoantibodies complicates transfusion therapy in thalassemia patients. These antibodies ultimately increase the need for blood and intensify transfusion complications. There is a scanty data on the frequency of RBC alloimmunization and autoimmunization in Egyptian β thalassemia patients as pretransfusion antibody screening is not routinely performed. We studied the frequency of alloimmunization and autoimmunization among 200 multiply transfused β thalassemia patients and investigated the factors that possibly affect antibody formation. Of the 200 patients in our study, 94 were males and 106 females, with the age range of 2–37 years. Alloantibodies were detected in 36 (18%) of the patients, while autoantibodies were detected in 33 (16.5%). The dominant alloantibodies were directed against Kell (33%) and Rh (24.4%) groups. Alloimmunization had a significant relationship with treatment duration and the frequency of transfusion (P = 0.007, 0.001, respectively). The presence of autoantibodies was significantly related to age (P = 0.001), total number of transfused units (P = 0.000) and splenectomy (P = 0.000). The high prevalence of alloimmunization in the study population disclosed the need for providing phenotypically matched cells for selective antigens especially for Kell and Rh subgroups to reduce risk of alloimmunization and increase the efficiency of blood transfusion.

Compound Heterozygosity for a Novel Mutation Codon 104 (-A) (HBB: c.313delA) and Codons 41/42 (-CTTT) (HBB: c.126_129delCTTT) Leading to β-Thalassemia Major in a Chinese Family

β-Thalassemia (β-thal) is a hereditary blood disorder characterized by the reduced or absent synthesis of β-globin chains. Here, we report a case of severe thalassemia with compound heterozygosity for a novel deletion mutation at codon 104 (-A) (HBB: c.313delA) and codons 41/42 (-CTTT) (HBB: c.126_129delCTTT) on the β-globin gene (HBB), and a coinheritance of the -α^4.2 (leftward) deletion on the α-globin gene cluster. The proband was a 12-year-old boy, and four other family members were involved in this study. This novel frameshift mutation caused classical β-thal trait in the heterozygote and a transfusion-dependent form of β-thal major (β-TM) in compound heterozygosity with other β⁰ mutations.

Prenatal Diagnosis and Screening of Thalassemia Mutations in Bangladesh: Presence of Rare Mutations

Thalassemia is the most common congenital monogenic disorder in Bangladesh. Prenatal diagnosis (PND) and pregnation termination of an affected child is one of the best options to reduce the burden of thalassemic children. This article reports the results of DNA analyses of chorionic villus sampling (CVS) and amniocentesis of fetuses of mothers who came to the thalassemia center of Dhaka Shishu (Children) Hospital, Dhaka, Bangladesh. DNA analysis was done by real-time polymerase chain reaction (qPCR) and Sanger sequencing. Maternal contamination was ruled out by variable number of tandem repeats (VNTRs). A total of 232 samples were analyzed. Hb E (HBB: c.79G>A)/β-thalassemia (Hb E/β-thal) was the most common type of thalassemia seen in 32 samples (13.79%) followed by β-thal major (β-TM) in 10 cases (4.31%). Molecular characterization of the most predominant mutation was IVS-I-5 (G>A) (HBB: c.92+5G>C). The analysis also revealed five rare mutations: IVS-II-654 (C>T) (HBB: c.316-197C>T), IVS-II-1 (G>A) (HBB: c.315+5G>A), codon 44 (-C) (HBB: c.135delC), -86 (C>A) (HBB: c.-136C>A) and codons 14/15 (+G) (HBB: c.45_46insG), which have not been reported previously in Bangladesh. This study provides important information for PND and will help in the development of similar diagnostic programs for other DNA centers in Bangladesh.

Changing patterns in the epidemiology of β-thalassemia

β‐thalassemia major is an inherited hemoglobinopathy that requires lifelong red blood cell transfusions and iron chelation therapy to prevent complications due to iron overload. Traditionally, β‐thalassemia has been more common in certain regions of the world such as the Mediterranean, Middle East, and Southeast Asia. However, the prevalence of β‐thalassemia is increasing in other regions, including Northern Europe and North America, primarily due to migration. This review summarizes the available data on the changing incidence and prevalence of β‐thalassemia as well as factors influencing disease frequency. The data suggest that the epidemiology of β‐thalassemia is changing: Migration has increased the prevalence of the disease in regions traditionally believed to have a low prevalence, while, at the same time, prevention and screening programs in endemic regions have reduced the number of affected individuals. Various approaches to prevention and screening have been used. Region‐specific prevention and treatment programs, customized to align with local healthcare resources and cultural values, have been effective in identifying patients and carriers and providing information and care. Significant challenges remain in universally implementing these programs.

Relative and Absolute Quantification of Aberrant and Normal Splice Variants in HBBIVSI-110 (G > A) β-Thalassemia

The β-thalassemias are an increasing challenge to health systems worldwide, caused by absent or reduced β-globin (HBB) production. Of particular frequency in many Western countries is HBBIVSI-110(G > A) β-thalassemia (HGVS name: HBB:c.93-21G > A). Its underlying mutation creates an abnormal splice acceptor site in the HBB gene, and while partially retaining normal splicing of HBB, it severely reduces HBB protein expression from the mutant locus and HBB loci in trans. For the assessment of the underlying mechanisms and of therapies targeting β-thalassemia, accurate quantification of aberrant and normal HBB mRNA is essential, but to date, has only been performed by approximate methods. To address this shortcoming, we have developed an accurate, duplex reverse-transcription quantitative PCR assay for the assessment of the ratio and absolute quantities of normal and aberrant mRNA species as a tool for basic and translational research of HBBIVSI-110(G > A) β-thalassemia. The method was employed here to determine mRNA ratios and quantities in blood and primary cell culture samples and correlate them with HBB protein levels. Moreover, with its immediate utility for β-thalassemia and the mutation in hand, the approach can readily be adopted for analysis of alternative splicing or for quantitative assays of any disease-causing mutation that interferes with normal splicing.

CRISPR-mediated gene modification of hematopoietic stem cells with beta-thalassemia IVS-1-110 mutation

Background

β-Thalassemias represent a group of genetic disorders caused by human hemoglobin beta (HBB) gene mutations. The radical curative approach is to correct the mutations causing the disease. CRISPR-CAS9 is a novel gene-editing technology that can be used auspiciously for the treatment of these disorders. The study aimed to investigate the utility of CRISPR-CAS9 for gene modification of hematopoietic stem cells in β-thalassemia with IVS-1-110 mutation.

Methods and results

We successfully isolated CD34⁺ cells from peripheral blood of β-thalassemia patients with IVS-1-110 mutation. The cells were transfected with Cas9 endonuclease together with guide RNA to create double-strand breaks and knock out the mutation. The mutation-corrected CD34⁺ cells were subjected to erythroid differentiation by culturing in complete media containing erythropoietin.

Conclusion

CRISPR/Cas-9 is an effective tool for gene therapy that will broaden the spectrum of therapy and potentially improve the outcomes of β-thalassemia.

Using LIBS as a diagnostic tool in pediatrics beta-thalassemia

Beta-thalassemia major is a common inherited single-gene disorder. Thalassemic patients are at risk of changes in some important trace elements. To detect alteration of iron, copper, zinc, and calcium serum levels in beta-thalassemia major patients, laser-induced breakdown spectroscopy (LIBS) was used. This study was conducted on 40 beta-thalassemia major and 40 healthy young patients (age: 12-18 years old; male:female = 1:1). Venous blood samples were collected from both groups and analyzed for the serum levels of iron, calcium, zinc, and copper by exposing the samples to LIBS. The intensities of the tested elements were detected using the Kestrel Spec computer software and analyzed with an SPSS 25 program. Thalassemic patients had significantly higher serum iron (p = < 0.001) and copper (p = < 0.005) while they had significantly lower serum zinc (p = < 0.005) and calcium (p= > 0.005) when compared with control. Also, thalassemic patients had significantly lower body weight and height as they were less than the 3rd percentile by 82.5% and p < 0.001. LIBS is a safe and efficient tool to detect alteration of some serum trace elements in beta-thalassemia patients.

Effect of Mutations on mRNA and Globin Stability: The Cases of Hb Bernalda/Groene Hart and Hb Southern Italy

We identified two unstable variants in the third exon of α-globin genes: Hb Bernalda/Groene Hart (HBA1:c.358C>T), and Hb Caserta (HBA2:c.79G>A) in cis to Hb Sun Prairie (HBA2:c.391G>C), also named Hb Southern Italy. These mutations occurred in the H helix of the α-globin that is involved in heme contacting, specific recognition of α-hemoglobin-stabilizing protein (AHSP), and α₁β₁ interactions. The carriers showed α-thalassemia phenotype, but one also jaundice and cholelithiasis. Molecular identification of clusters of families in Southern Italy encouraged molecular characterization of mRNA, globin chain analyses, molecular modeling studies, and comparison with globin variants to understand the mechanisms causing the α-thalassemia phenotype. A normal amount of Hb Bernalda/Groene Hart mRNA were found, and molecular modeling highlighted additional H bonds with AHSP. For Hb Southern Italy, showing an unexpected α/β biosynthetic ratio typical of the β-thalassemia type, two different molecular mechanisms were shown: Reduction of the variant mRNA, likely due to the No-Go Decay for the presence of unused triplet ACG at cod 26, and protein instability due to the impairment of AHSP interaction. The UDP glucuronosyltransferase 1A (UGT1A1) genotyping was conclusive in the case of jaundice and cholelithiasis. Multiple approaches are needed to properly identify the mechanisms leading to unstable variants and the effect of a mutation.

Hemoglobin variants in southern China: results obtained during the measurement of glycated hemoglobin in a large population

Objectives

Hemoglobin (Hb) variant is one of the most common monogenic inherited disorders. We aimed to explore the prevalence and hematological and molecular characteristics of Hb variants in southern China.

Methods

We collected blood samples from all patients with suspected variants found during HbA1c measurement via a cation-exchange high-performance liquid chromatography system (Bio-Rad Variant II Turbo 2.0) or a capillary electrophoresis method (Sebia Capillarys). Hematological analysis, Sanger sequencing, and gap-PCR were performed for these samples.

Results

Among the 311,024 patients tested, we found 1,074 Hb variant carriers, including 823 identified using Capillarys and 251 using Variant II Turbo 2.0, with a total carrier rate of 0.35%. We discovered 117 types of Hb variants (52 HBB, 47 HBA, and 18 HBD mutations) containing 18 new mutations. The most common variant found was Hb E, followed by Hb New York, Hb J-Bangkok, Hb Q-Thailand, Hb G-Coushatta, Hb G-Honolulu, Hb G-Taipei, and Hb Broomhill. Most heterozygotes for the Hb variant exhibited normal hematological parameters. However, most patients with compound heterozygotes for the Hb variant and thalassemia showed varied degrees of microcytic hypochromic anemia.

Conclusions

The prevalence of hemoglobin variants remains high and exhibits genetic diversity and widespread distribution in the population of southern China.

β-Thalassemia pathogenic variants in a cohort of children from the East African coast

BACKGROUND

β-Thalassemia is rare in sub-Saharan Africa. Previous studies have suggested that it is limited to specific parts of West Africa. Based on hemoglobin A2 (HbA2 ) concentrations measured by HPLC, we recently speculated that β-thalassemia might also be present on the East African coast of Kenya. Here, we follow this up using molecular methods.

METHODS

We used raised hemoglobin A2 (HbA2 ) values (> 4.0% of total Hb) to target all HbAA members of a cohort study in Kilifi, Kenya, for HBB sequencing for β-thalassemia (n = 99) together with a sample of HbAA subjects with lower HbA2 levels. Because HbA2 values are artifactually raised in subjects carrying sickle hemoglobin (HbS) we sequenced all participants with an HPLC pattern showing HbS without HbA (n = 116) and a sample with a pattern showing both HbA and HbS.

RESULTS

Overall, we identified 83 carriers of four separate β-thalassemia pathogenic variants: three β0 -thalassemia [CD22 (GAA→TAA), initiation codon (ATG→ACG), and IVS1-3' end del 25bp] and one β+ -thalassemia pathogenic variants (IVS-I-110 (G→A)). We estimated the minimum allele frequency of all variants combined within the study population at 0.3%.

CONCLUSIONS

β-Thalassemia is present in Kilifi, Kenya, an observation that has implications for the diagnosis and clinical care of children from the East Africa region.

Comparative targeting analysis of KLF1, BCL11A, and HBG1/2 in CD34+ HSPCs by CRISPR/Cas9 for the induction of fetal hemoglobin

β-hemoglobinopathies are caused by abnormal or absent production of hemoglobin in the blood due to mutations in the β-globin gene (HBB). Imbalanced expression of adult hemoglobin (HbA) induces strong anemia in patients suffering from the disease. However, individuals with natural-occurring mutations in the HBB cluster or related genes, compensate this disparity through γ-globin expression and subsequent fetal hemoglobin (HbF) production. Several preclinical and clinical studies have been performed in order to induce HbF by knocking-down genes involved in HbF repression (KLF1 and BCL11A) or disrupting the binding sites of several transcription factors in the γ-globin gene (HBG1/2). In this study, we thoroughly compared the different CRISPR/Cas9 gene-disruption strategies by gene editing analysis and assessed their safety profile by RNA-seq and GUIDE-seq. All approaches reached therapeutic levels of HbF after gene editing and showed similar gene expression to the control sample, while no significant off-targets were detected by GUIDE-seq. Likewise, all three gene editing platforms were established in the GMP-grade CliniMACS Prodigy, achieving similar outcome to preclinical devices. Based on this gene editing comparative analysis, we concluded that BCL11A is the most clinically relevant approach while HBG1/2 could represent a promising alternative for the treatment of β-hemoglobinopathies.

Hemoglobin Ottawa (HBA2:c.46G>C) and β+ Thalassemia (HBB:c.-138C>T) Detected in an Indian Male by Capillary Zone Electrophoresis

Hemoglobin (Hb) Ottawa [α15(A13)Gly>Arg], also known as Hb Siam, results from GGT>CGT mutation in codon 15 of either HBA1 or HBA2. Hb Ottawa carriers typically have normal hematology but when the variant is coinherited with either α or β thalassemia, microcytic red cell indices were observed. The percentage of variant detected using routine methodology was variable (14-33%), with a higher percentage found when co-inherited with an abnormal α-globin genotype. The case presented here involved an Indian male with microcytic red cell indices, who was heterozygous for Hb Ottawa (HBA2:c.46G>C) and β+ thalassemia (HBB:c.-138C>T). This case represents the first reported finding of Hb Ottawa in the Indian population, as well as the first time capillary zone electrophoresis (CZE) has been used to identify the variant. The abnormal red cell indices were attributed to co-inheritance of β+ thalassemia mutation (HBB:c.-138C>T), which alters binding of transcriptional factors to the HBB promoter and reduces transcription from the allele. The mild β+ thalassemia mutation has commonly been found in the Indian population.

Comparative analysis of lentiviral gene transfer approaches designed to promote fetal hemoglobin production for the treatment of β-hemoglobinopathies

β-Hemoglobinopathies are among the most common single-gene disorders and are caused by different mutations in the β-globin gene. Recent curative therapeutic approaches for these disorders utilize lentiviral vectors (LVs) to introduce a functional copy of the β-globin gene into the patient's hematopoietic stem cells. Alternatively, fetal hemoglobin (HbF) can reduce or even prevent the symptoms of disease when expressed in adults. Thus, induction of HbF by means of LVs and other molecular approaches has become an alternative treatment of β-hemoglobinopathies. Here, we performed a head-to-head comparative analysis of HbF-inducing LVs encoding for: 1) IGF2BP1, 2) miRNA-embedded shRNA (shmiR) sequences specific for the γ-globin repressor protein BCL11A, and 3) γ-globin gene. Furthermore, two novel baboon envelope proteins (BaEV)-LVs were compared to the commonly used vesicular-stomatitis-virus glycoprotein (VSV-G)-LVs. Therapeutic levels of HbF were achieved for all VSV-G-LV approaches, from a therapeutic level of 20% using γ-globin LVs to 50% for both IGF2BP1 and BCL11A-shmiR LVs. Contrarily, BaEV-LVs conferred lower HbF expression with a peak level of 13%, however, this could still ameliorate symptoms of disease. From this thorough comparative analysis of independent HbF-inducing LV strategies, we conclude that HbF-inducing VSV-G-LVs represent a promising alternative to β-globin gene addition for patients with β-hemoglobinopathies.

Genetic Regulation of Redox Balance in β-Thalassemia Trait

β-Thalassemia (β-thal) trait is a heterogeneous group of genetic defects leading to decreased β-globin production, ineffective erythropoiesis, and oxidative stress. The aim is to evaluate the cytoprotective response, at transcriptional and systemic levels, of the variations of global redox balance in β-thal trait patients. Sixty-six subjects (40 healthy and 26 with β-thal trait) were analyzed at the Universidad Nacional de Tucumán, Tucumán, Argentina, between 2016 and 2017. The following parameters were evaluated: complete blood count, iron status, hemoglobin (Hb) electrophoresis, Hb A₂, thiobarbituric acid reactive species (TBARS), serum catalase (CAT), and superoxide dismutase (SOD) activity, FOXO3a, NRF2, SOD, PRDX2, CAT, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) gene expression. The β-thal trait group showed a decrease in Hb levels, MCV, and MCH with higher TBARS levels. The SOD activity was significantly increased by 32.0% in β-thal trait patients respect to the control group. Relative expression of NRF2 was 4.7-fold higher in β-thal trait than in the control group, while FOXO3a expression was similar in both groups. The SOD, PRDX2, and proinflammatory cytokines transcriptional expression was significantly upregulated in β-thal trait patients. This is the first study on the genetic regulation of redox balance in β-thal trait patients in which interesting modifications were observed in the transcript levels of some redox regulators that could be associated with changes in the erythrocyte proteome in this disorder. A better understanding of the pathophysiological mechanisms present in these heterozygous patients would allow adequate therapy in situations such as growth, pregnancy, or high performance sports, favoring a personalized treatment.

The prevalence of hepatitis C virus infection in β-thalassemia patients in Pakistan: a systematic review and meta-analysis

Background

Hepatitis C virus infection is the most commonly reported bloodborne infection in Pakistan. Frequent blood transfusions in β-thalassemia patients expose them to a high risk of HCV infection. The purpose of this paper is to summarise the current data on the prevalence of HCV infection in β-thalassemia patients in Pakistan by using a systematic review and meta–analysis.

Methods

PubMed, EMBASE, Web of Sciences, the Cochrane Library, Directory of Open Access Journal and local databases were systematically searched for studies published between January 1st, 1995 and May 31st, 2019. Meta-analysis was performed using the DerSimonian and Laird random-effects models with inverse variance weighting. The presence of publication bias was tested by Egger test, and the methodological quality of each included article was evaluated by the STROBE.

Results

We identified a total of 229 potential studies, of which 27 studies were finally considered in the meta-analysis. The pooled prevalence of HCV in β-thalassemia patients in Pakistan was 36.21% (95% CI: 28.98–43.75%) based on 5789 β-thalassemia patients, but there was considerable heterogeneity. Meta-analysis estimated the HCV prevalence among the β-thalassemia patients at 45.98% (95% CI: 38.15–53.90%) in Punjab, 31.81% (95% CI: 20.27–44.59%) in Sindh, and 28.04% (95% CI: 13.58–45.26%) in Khyber Pakhtunkhwa. Meta–regression analysis showed that geographical location was a key source of heterogeneity.

Conclusions

The pooled prevalence of HCV in β-thalassemia patients in Pakistan was more than one in three, and higher than in neighbouring countries. It varies regionally within the country. With the use of standard prevention procedures during blood transfusion, the risk of HCV transmission in β-thalassemia patients could be controlled and the prevalence of HCV in β-thalassemia patients reduced.

Improved efficiency and patient safety through bespoke electronic thalassaemia care module

Objectives

To investigate the impact of electronic medical record (EMR) on improvement of healthcare parameters in a thalassaemia centre located at the Fujairah Hospital, Fujairah, UAE.

Materials and methods

A hospital-wide EMR system (Wareed) was implemented across the hospitals in the Ministry of Health and Prevention, UAE, including two major thalassaemia centres. We aim to investigate the impact of this intervention across a number of healthcare parameters over two quarters (before and after implementation of the system).

Results

Since preimplementation data were not available for one facility, comparisons were made between parameters in two quarters in Fujairah hospital only. After introduction of Wareed, we found an increase in number of appointments (12%) (p=0.00), decrease in the number of appointment cancellations due to non-availability of blood products (p=0.02), reduction in the time to cannulation (p=0.00), decrease in number of physician days (p=0.295) among other parameters observed.

Discussion

Research shows that EMR systems have a positive impact on reduction in medical expenditure, improvement of healthcare quality and overall health outcomes. thalassaemia is highly prevalent in the Middle Eastern countries and drains the medical, social and financial resources of these nations. Our study is an attempt to create an insight into the difference in healthcare parameters before and after introduction of the system.

Conclusion

Being the first of a kind in this region, our study created favourable evidence that introduction of an EMR has an overall positive impact on the healthcare delivery system for thalassaemia care.

Hb S/-Thalassemia in the REDS-III Brazil Sickle Cell Disease Cohort: Clinical, Laboratory and Molecular Characteristics

We described the clinical, laboratory and molecular characteristics of individuals with Hb S (HBB: c.20A>T)/β-thalassemia (Hb S/β-thal) participating in the Recipient Epidemiology and Donor Evaluation Study (REDS-III) Brazil Sickle Cell Disease cohort. HBB gene sequencing was performed to genotype each β-thal mutation. Patients were classified as Hb S/β⁰-thal, Hb S/β⁺-thal-severe or Hb S/β⁺-thal based on prior literature and databases of hemoglobin (Hb) variants. Characteristics of patients with each β-thal mutation were described and the clinical profile of patients grouped into Hb S/β⁰-thal, Hb S/β⁺-thal and Hb S/β⁺-thal-severe were compared. Of the 2793 patients enrolled, 84 (3.0%) had Hb S/β⁰-thal and 83 (3.0%) had Hb S/β⁺-thal; 40/83 (48.2%) patients with Hb S/β⁺-thal had mutations defined as severe. We identified 19 different β-thal mutations, eight Hb S/β⁰-thal, three Hb S/β⁺-thal-severe and eight Hb S/β⁺-thal. The most frequent β⁰ and β⁺ mutations were codon 39 (HBB: c.118C>T) and IVS-I-6 (T>C) (HBB: c.92+6T>C), respectively. Individuals with Hb S/β⁰-thal had a similar clinical and laboratory phenotype when compared to those with Hb S/β⁺-thal-severe. Individuals with Hb S/β⁺-thal-severe had significantly lower total Hb and Hb A levels and higher Hb S, white blood cell (WBC) count, platelets and hemolysis markers when compared to those with Hb S/β⁺-thal. Likewise, individuals with Hb S/β⁺-thal-severe showed a significantly higher occurrence of hospitalizations, vaso-occlusive events (VOE), acute chest syndrome (ACS), splenic sequestration, blood utilization, and hydroxyurea (HU) therapy.

Molecular Heterogeneity of β-Thalassemia in the Kohat Region, Khyber Pakhtunkhwa Province, Pakistan

The present study was intended to report the incidence of the most frequently occurring β-thalassemia (β-thal) mutations in the Kohat region [Khyber Pakhtunkhwa (KP) Province, Pakistan], their inheritance pattern in patients, and consanguinity in the parents. Moreover, this study could provide valuable information regarding thalassemia diagnoses such as prenatal diagnosis (PND), genetic counseling and carrier screening for controlling the affected births in the population. During this study, 160 peripheral blood samples of affected patients, their parents and siblings were collected from 25 discrete families having at least one child needing regular blood transfusions from different areas of the Kohat region. β-Thalassemia mutations found in the population were screened via the amplification refractory mutation system-polymerase chain reaction (ARMS-PCR). A total of 320 alleles was evaluated for the presence of six β-thal mutations. Of these six β-thal mutations, the frameshift codons (FSC) 8/9 (+G) (HBB: c.27_28insG) was found to be the most frequent in the studied population, and more interestingly, followed by IVS-I-5 (G>C) (HBB: c.92+5G>C) and FSC 5 (-CT) (HBB: c.17_18delCT). The findings of the present study show differences with previous results from other regions of the Pashtun population, which demarcates the heterogeneity in mutations found in the Pashtun ethnicity. These observations may help in implementing parental meetings about disease recurrence in future, large scale mutation screening and PND for the population of the Kohat region and also the whole Pashtun ethnicity.

Dominant β-thalassaemia with unusually high Hb A2 and Hb F caused by βCD121(-G) (HBB:c.364delG) in exon 3 of β-globin gene

We describe a dominant β-thalassaemia caused by a deletion of G at nucleotide position 364 in exon 3 of the β-globin gene. The heterozygosity of this mutation was found in a 36-year-old Thai patient who had moderate hypochromic microcytic anaemia with haemolytic blood picture. Haemoglobin (Hb) analysis revealed relatively higher Hbs A₂ (6.8%) and F (4.7%) as compared with those of β⁰-thalassaemia (n=278) and β⁺-thalassaemia (n=55) carriers in our series. Secondary structure prediction of the elongated β-globin chain showed that the α-helix at the C-terminal is disrupted dramatically by the random coil and β-sheet, which should result in a highly unstable β-globin variant, undetectable in peripheral blood and a dominant clinical phenotypic feature.

HbS/β+ thalassemia: Really a mild disease? A National survey from the AIEOP Sickle Cell Disease Study Group with genotype-phenotype correlation

OBJECTIVES

HbS/β+ patients' presence in Italy increased due to immigration; these patients are clinically heterogeneous, and specific guidelines are lacking. Our aim is to describe a cohort of HbS/β+ patients, with genotype-phenotype correlation, in order to offer guidance for clinical management of such patients.

METHODS

Retrospective cohort study of HbS/β+ patients among 15 AIEOP Centres.

RESULTS

A total of 41 molecularly confirmed S/β+ patients were enrolled (1-55 years, median 10.9) and classified on β+ mutation: IVS-I-110, IVS-I-6, promoter, and "others." Prediagnostic events included VOC 16/41 (39%), ACS 6/41 (14.6%), sepsis 3/41 (3.7%), and avascular necrosis 3/41 (7,3%). Postdiagnostic events were VOC 22/41 (53.6% %), sepsis 4/41 (9.7%), ACS 4/41 (9.7%), avascular necrosis 3/41 (7.3%), aplastic crisis 2/41 (4.8%), stroke 1/41 (2.4%), ACS 1/41 (2.4%), and skin ulcerations 1/41 (2.4%). The IVS-I-110 group presented the lowest median age at first SCD-related event (P = .02 vs promoter group) and the higher median number of severe events/year (0.26 events/patient/year) (P = .01 vs IVS-I-6 and promoter groups). Promoter group presented a specific skeletal phenotype. Treatment regimen applied was variable among the centers.

CONCLUSIONS

HbS/β+ is not always a mild disease. Patients with IVS-I-110 mutation could benefit from a standard of care like SS and S/β° patients. Standardization of treatment is needed.

Molecular and geographical heterogeneity of hemoglobinopathy mutations in Azerbaijanian populations

With the carrier rate of 4%-8.6%, β-thalassemia is one of the most prevalent hereditary disorders in Azerbaijan. Taking into consideration the high frequency of β-thalassemia as well as the occurrences of several other hemoglobinopathies, we conducted a large genotyping study to investigate the mutational background of common hemoglobinopathies in the country. Α- and β-globin genes were evaluated in the carriers of mutations identified via hematological indices and hemoglobin fractions (n = 1,757). Genotyping of β-thalassemia carriers identified through population screening revealed 32 mutations, with codon 8 [-AA]-34.96%, IVS-II-1 [G > A]-16.35%, and IVS-I-110 [G > A]-10.12% leading the spectrum. Analysis of associations of β-thalassemia mutations with geographical regions of the country identified the strongest association between codon 8 [-AA] and Shaki-Zaqatala, and codon 5 [-CT] in Mountainous Shirvan regions (ri > 6.00; p < 0.05). HbS, HbD-Punjab, and HbE were the most prevalent among our variant hemoglobin cohort, commonly inherited in compounds with β-thalassemia than in the homozygous state. We identified nine α-thalassemia mutations, 20.5 kb and 3.7 kb deletions together accounting for 74% of the spectrum. Point mutations of α-thalassemia were less common among our observations and were mainly inherited in compounds with deletions. Our results allow a better understanding of the wide spectrum of mutations in Azerbaijan and highlights the high heterogeneity of hemoglobinopathies in the local population.

The Scope for Thalassemia Gene Therapy by Disruption of Aberrant Regulatory Elements

The common IVSI-110 (G>A) β-thalassemia mutation is a paradigm for intronic disease-causing mutations and their functional repair by non-homologous end joining-mediated disruption. Such mutation-specific repair by disruption of aberrant regulatory elements (DARE) is highly efficient, but to date, no systematic analysis has been performed to evaluate disease-causing mutations as therapeutic targets. Here, DARE was performed in highly characterized erythroid IVSI-110(G>A) transgenic cells and the disruption events were compared with published observations in primary CD34⁺ cells. DARE achieved the functional correction of β-globin expression equally through the removal of causative mutations and through the removal of context sequences, with disruption events and the restriction of indel events close to the cut site closely resembling those seen in primary cells. Correlation of DNA-, RNA-, and protein-level findings then allowed the extrapolation of findings to other mutations by in silico analyses for potential repair based on the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) 9, Cas12a, and transcription activator-like effector nuclease (TALEN) platforms. The high efficiency of DARE and unexpected freedom of target design render the approach potentially suitable for 14 known thalassemia mutations besides IVSI-110(G>A) and put it forward for several prominent mutations causing other inherited diseases. The application of DARE, therefore, has a wide scope for sustainable personalized advanced therapy medicinal product development for thalassemia and beyond.

Genetic Modifiers at the Crossroads of Personalised Medicine for Haemoglobinopathies

Haemoglobinopathies are common monogenic disorders with diverse clinical manifestations, partly attributed to the influence of modifier genes. Recent years have seen enormous growth in the amount of genetic data, instigating the need for ranking methods to identify candidate genes with strong modifying effects. Here, we present the first evidence-based gene ranking metric (IthaScore) for haemoglobinopathy-specific phenotypes by utilising curated data in the IthaGenes database. IthaScore successfully reflects current knowledge for well-established disease modifiers, while it can be dynamically updated with emerging evidence. Protein-protein interaction (PPI) network analysis and functional enrichment analysis were employed to identify new potential disease modifiers and to evaluate the biological profiles of selected phenotypes. The most relevant gene ontology (GO) and pathway gene annotations for (a) haemoglobin (Hb) F levels/Hb F response to hydroxyurea included urea cycle, arginine metabolism and vascular endothelial growth factor receptor (VEGFR) signalling, (b) response to iron chelators included xenobiotic metabolism and glucuronidation, and (c) stroke included cytokine signalling and inflammatory reactions. Our findings demonstrate the capacity of IthaGenes, together with dynamic gene ranking, to expand knowledge on the genetic and molecular basis of phenotypic variation in haemoglobinopathies and to identify additional candidate genes to potentially inform and improve diagnosis, prognosis and therapeutic management.

Curating the gnomAD database: Report of novel variants in the globin-coding genes and bioinformatics analysis

Massive parallel sequencing technologies are facilitating the faster identification of sequence variants with the consequent capability of untangling the molecular bases of many human genetic syndromes. However, it is not always easy to understand the impact of novel variants, especially for missense changes, which can lead to a spectrum of phenotypes. This study presents a custom-designed multistep methodology to evaluate the impact of novel variants aggregated in the genome aggregation database for the HBB, HBA2, and HBA1 genes, by testing and improving its performance with a dataset of previously described alterations affecting those same genes. This approach scored high sensitivity and specificity values and showed an overall better performance than sequence-derived predictors, highlighting the importance of protein conformation and interaction specific analyses in curating variant databases. This study also describes the strengths and limitations of these structural studies and allows identifying residues in the globin chains more prone to tolerate substitutions.

LOVD-DASH: A comprehensive LOVD database coupled with diagnosis and an at-risk assessment system for hemoglobinopathies

Hemoglobinopathies are the most common monogenic disorders worldwide. Substantial effort has been made to establish databases to record complete mutation spectra causing or modifying this group of diseases. We present a variant database which couples an online auxiliary diagnosis and at-risk assessment system for hemoglobinopathies (DASH). The database was integrated into the Leiden Open Variation Database (LOVD), in which we included all reported variants focusing on a Chinese population by literature peer review-curation and existing databases, such as HbVar and IthaGenes. In addition, comprehensive mutation data generated by high-throughput sequencing of 2,087 hemoglobinopathy patients and 20,222 general individuals from southern China were also incorporated into the database. These sequencing data enabled us to observe disease-causing and modifier variants responsible for hemoglobinopathies in bulk. Currently, 371 unique variants have been recorded; 265 of 371 were described as disease-causing variants, whereas 106 were defined as modifier variants, including 34 functional variants identified by a quantitative trait association study of this high-throughput sequencing data. Due to the availability of a comprehensive phenotype-genotype data set, DASH has been established to automatically provide accurate suggestions on diagnosis and genetic counseling of hemoglobinopathies. LOVD-DASH will inspire us to deal with clinical genotyping and molecular screening for other Mendelian disorders.

The Spectrum of β-Thalassemia Mutations in Siirt Province, Southeastern Turkey

β-Thalassemia (β-thal) is the most common hereditary genetic blood disorder. The aims of this study were: (i) to determine the mutation types and the frequency of these mutations in β-thal patients to obtain the ethnic origins of the population in Siirt Province; (ii) to evaluate the pathogenicity of these mutations by performing in silico analysis; (iii) to reveal the genotype-phenotype correlation by comparing the clinical manifestation of our patients to the specific mutations in this population. This study included 34 patients (18 males and 16 females) with a mean age of 9.1 ± 3.6 years (range 3-16 years). All mutations were determined using sequence analysis methods, and the mutations were analyzed using bioinformatics tools. Thirteen different mutations were detected in the patients: IVI-I-110 (G>A) (HBB: c.93-21G>A) (38.9%); IVS-II-1 (G>A) (HBB: c.315_1G>A) (11.1%); -30 (T>A) (HBB: c.-80T>A) (9.25%) and IVS-I-1 (G>A) (HBB: c.92 + 1G>A) (9.25%), were the most common, and these mutations constituted 68.5% of the cases. Missense codon 6 (A>T) (HBB: c.20A>T) was not pathogenic; however, all the intronic mutations (IVS-I-1, IVS-I-110, IVS-II-1) and frameshift mutations [codon 44 (-C) (HBB: c.135delC) and codons 36/37 (-T) (HBB: c.112delT)] resulted in disease. These mutations can be used to determine the ethnic origin of the Siirt population and, in affected pregnant women, to develop prenatal strategies. A fatal phenotype can be identified by in silico analysis; however, mutations that are unknown prior to marriage, pregnancy, and childbirth or new mutations can be less accurately identified.

Hb Alcorn County: A β-Globin Variant [β40(C6)Arg→Thr; HBB: c.122G>C (p.Arg41Thr)] with Increased Oxygen Affinity

We describe Hb Alcorn County, a heterozygous hemoglobin (Hb) variant, in a 6-month-old Hispanic male and his mother. DNA sequencing demonstrated a mutation on the HBB gene [β40(C6)Arg→Thr; HBB: c.122G>C (p.Arg41Thr)], predictive of a substitution of arginine to threonine at position 40 of the β-globin protein. This amino acid substitution involves the α1β2 contact and occurs at the same position as Hb Austin [β40(C6)Arg→Ser; HBB: c.[123G>C or 123G>T] (p.Arg41Ser)] and Hb Athens-GA [β40(C6)Arg→Lys; HBB: c.122G>A (p.Arg41Lys)], both of which show increased oxygen affinity.

Rare Opportunities: CRISPR/Cas-Based Therapy Development for Rare Genetic Diseases

Rare diseases pose a global challenge, in that their collective impact on health systems is considerable, whereas their individually rare occurrence impedes research and development of efficient therapies. In consequence, patients and their families are often unable to find an expert for their affliction, let alone a cure. The tide is turning as pharmaceutical companies embrace gene therapy development and as serviceable tools for the repair of primary mutations separate the ability to create cures from underlying disease expertise. Whereas gene therapy by gene addition took decades to reach the clinic by incremental disease-specific refinements of vectors and methods, gene therapy by genome editing in its basic form merely requires certainty about the causative mutation. Suddenly we move from concept to trial in 3 years instead of 30: therapy development in the fast lane, with all the positive and negative implications of the phrase. Since their first application to eukaryotic cells in 2013, the proliferation and refinement in particular of tools based on clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas) prokaryotic RNA-guided nucleases has prompted a landslide of therapy-development studies for rare diseases. An estimated thousands of orphan diseases are up for adoption, and legislative, entrepreneurial, and research initiatives may finally conspire to find many of them a good home. Here we summarize the most significant recent achievements and remaining hurdles in the application of CRISPR/Cas technology to rare diseases and take a glimpse at the exciting road ahead.

Genetic variation influencing hemoglobin levels and risk for anemia across populations

Hemoglobin (Hb) concentration is the outcome of the interaction between genetic variation and environmental factors, including nutritional status, sex, age, and altitude. Genetic diversity influencing this protein is complex and varies widely across populations. Variants related to abnormal Hb or altered characteristics of the erythrocytes increase the risk for anemia. The most prevalent are related to the inherited globin abnormalities affecting Hb production and structure. Malaria-endemic regions harbor the highest frequencies of variants associated with the most frequent monogenic diseases and the risk for nonnutritional anemia and are considered as public health problems. Variation in genes encoding for enzymes and membrane proteins in red blood cells also influence erythrocyte life span and risk for anemia. Most of these variants are rare. Interindividual variability of hematological parameters is also influenced by common genetic variation across the whole genome. Some of the identified variants are associated with Hb production, erythropoiesis, and iron metabolism. Specialized databases have been developed to organize and update the large body of available information on genetic variation related to Hb variation, their frequency, geographical distribution, and clinical significance. Our present review analyzed the underlying genetic factors that affect Hb concentrations, their clinical relevance, and geographical distribution across populations.

Identification of a novel pre-terminating mutation in human HBB gene as a cause of β0-thalassemia phenotype

Beta (β)-thalassemia (thal) is one of the most common genetic disorders of hemoglobin synthesis worldwide. Most cases of β-thal are caused by point mutations in hemoglobin subunit beta (HBB) gene, and only a minority of cases are caused by missing mutations of HBB gene. In this study, a 31-year-old pregnant woman with a typical thal phenotype was admitted at Fujian Provincial Maternity and Children's Hospital for prenatal diagnosis. Her father also presented with a typical thal phenotype, while the other members in the proband family were normal. Interestingly, Gap-PCR and reverse dot-blot hybridization assays showed that no mutation was found in the human HBA and HBB genes of the proband and her father. Subsequently, Sanger DNA sequencing identified a novel pre-terminating mutation, c.271 G>T [CD90 (GAG>TAG, Glu→stop codon)], in HBB gene from the proband and her father, while the other members in the proband family were normal. This mutation created a stop codon at amino acid 90 in exon 2 coding sequences of HBB gene, and led to a β⁰-thal phenotype. In summary, the present study is, to the best of our knowledge, the first to report a pre-terminating mutation, c.271 G>T [CD90 (GAG>TAG, Glu→stop codon)], in human HBB gene as a cause of β⁰-thal phenotype. This is important for clarifying the molecular mechanism of β⁰-thal and is useful for genetic counseling and prenatal screening.

Family planning practices in couples with children affected by β-thalassemia major and its relationship with their education: An epidemiological study

BACKGROUND

Although prevention the birth of children with β-thalassemia major (β-TM) is an important health issue, it is rarely explored. With this background, the study was designed to find family planning practices and related factors of couples with children affected by β-TM.

MATERIALS AND METHODS

This was a cross-sectional, observational study, conducted among 324 parents with children affected by β-TM attending a tertiary care health facility in Eastern India. Data were analyzed using univariate and multivariable logistic regression using SPSS.

RESULTS

Of 324 parents, 89.5% were sexually active, 44.8% of which were currently using family planning method to prevent the birth of another child with the oral contraceptive pill most preferred (46.9%) followed by tubectomy (33.9%). Those who were sexually active, but not desirous of a child were 223, of which 41.7% had the unmet need for family planning with religious belief (41.9%) being the most predominant reason followed by unaware of methods (26.9%). In multivariable analysis, religion, caste, per capita monthly income, mothers' education level, and working status were significant predictors of unmet need for family planning adjusted with others.

CONCLUSIONS

Burden of unmet need for family planning among the study population was alarmingly high. Parents of the thalassemic children should be counseled in easily comprehensible local language to increase the rate of contraception among them.

A novel mutation in the erythroid transcription factor KLF1 is likely responsible for ameliorating β-thalassemia major

We describe the identification of a novel missense mutation in the second zinc finger of KLF1 in two siblings who, based on their genotype, are predicted to suffer from beta thalassemia major but are, in fact, transfusion‐free and in good health. These individuals, as well as two additional members of the same family also carrying this KLF1 mutation, exhibit high levels of fetal hemoglobin (HbF). KLF1 is an erythroid transcription factor, which plays a critical role in the regulation of the developmental switch between fetal and adult hemoglobin by regulating the expression of a multitude of genes including that of BCL11A. The mutation appears to be the main candidate responsible for the beta thalassemia‐ameliorating effect as this segregates with the observed phenotype and also exogenous expression of the KLF1 mutant protein in human erythroid progenitor cells resulted in the induction of γ‐globin, without, however, affecting BCL11A levels. This report adds to the weight of evidence that heterozygous KLF1 mutations can ameliorate the severity of the β‐thalassemia major phenotype.

Editing aberrant splice sites efficiently restores β-globin expression in β-thalassemia

The thalassemias are compelling targets for therapeutic genome editing in part because monoallelic correction of a subset of hematopoietic stem cells (HSCs) would be sufficient for enduring disease amelioration. A primary challenge is the development of efficient repair strategies that are effective in HSCs. Here, we demonstrate that allelic disruption of aberrant splice sites, one of the major classes of thalassemia mutations, is a robust approach to restore gene function. We target the IVS1-110G>A mutation using Cas9 ribonucleoprotein (RNP) and the IVS2-654C>T mutation by Cas12a/Cpf1 RNP in primary CD34+ hematopoietic stem and progenitor cells (HSPCs) from β-thalassemia patients. Each of these nuclease complexes achieves high efficiency and penetrance of therapeutic edits. Erythroid progeny of edited patient HSPCs show reversal of aberrant splicing and restoration of β-globin expression. This strategy could enable correction of a substantial fraction of transfusion-dependent β-thalassemia genotypes with currently available gene-editing technology.

A Novel BaEVRless-Pseudotyped γ-Globin Lentiviral Vector Drives High and Stable Fetal Hemoglobin Expression and Improves Thalassemic Erythropoiesis In Vitro

It has previously been demonstrated that the self-inactivating γ-globin lentiviral vector GGHI can significantly increase fetal hemoglobin (HbF) in erythroid cells from thalassemia patients and thus improve the disease phenotype in vitro. In the present study, the GGHI vector was improved further by incorporating novel enhancer elements and also pseudotyping it with the baboon endogenous virus envelope glycoprotein BaEVRless, which efficiently and specifically targets human CD34⁺ cells. We evaluated the hypothesis that the newly constructed vector designated as GGHI-mB-3D would increase hCD34⁺ cell tropism and thus transduction efficiency at low multiplicity of infection, leading to increased transgene expression. High and stable HbF expression was demonstrated in thalassemic cells for the resulting GGHI-mB-3D/BaEVRless vector, exhibiting increased transduction efficiency compared to the original GGHI-mB-3D/VSVG vector, with a concomitant 91% mean HbF increase at a mean vector copy number per cell of 0.86 and a mean transduction efficiency of 56.4%. Transduced populations also exhibited a trend toward late erythroid, orthochromatic differentiation and reduced apoptosis, a further indication of successful gene therapy treatment. Monitoring expression of ATG5, a key link between autophagy and apoptosis, it was established that this correction correlates with a reduction of enhanced autophagy activation, a typical feature of thalassemic polychromatophilic normoblasts. This work provides novel mechanistic insights into gene therapy-mediated correction of erythropoiesis and demonstrates the beneficial role of BaEVRless envelope glycoprotein compared to VSVG pseudotyping and of the novel GGHI-mB-3D/BaEVRless lentiviral vector for enhanced thalassemia gene therapy.

Molecular characterisation of haemoglobin E-Udon Thani (HBB:c.[79G>A;92+7A>G]): a novel form of Hb E-β-thalassaemia syndrome

Interaction of βE-globin gene with an in trans β-thalassaemia gene leads to thalassaemia syndrome, known as haemoglobin (Hb) E-β-thalassaemia disease, with variable clinical and haematological severity. Here, we reported for the first time the Hb E-β-thalassaemia syndrome caused alternatively by an in cis interaction of βE and a novel IVSI#7;A>G mutation, namely the Hb E-Udon Thani (HBB:c.[79G>A;92+7 A>G]). The syndrome was found in an adult Thai man (32) who was generally healthy but had an unexplained hypochromic microcytosis. Hb analysis identified heterozygous Hb E with very low Hb E expression (3.1%) and elevated Hb A2 (5.7%). Final diagnosis was made on DNA analysis, which confirmed a double mutation in a single β-globin gene of the patient. A multiplex allele-specific PCR assay was developed for use in the screening of this novel form of Hb E-β-thalassaemia in the population.

Codon 14 (+T) (HBB: c.44_45insT): a Rare β-Thalassemia Mutation Reported Only in Azerbaijan

Codon 14 (+T) (HBB: c.44_45insT) is a very rare β-thalassemia (β-thal) mutation previously reported in three β-thal major (β-TM) patients of Azerbaijani origin. None of the previous reports described the genotype-phenotype correlation of the mutation. We here report the first case of homozygous codon 14 together with data of the heterozygous parents.

Hb Palencia: a novel δβδ-type two-way fusion variant with β-globin-like expression levels

AIMS

Fusion proteins of unequal recombination events at the β-globin locus have pathological effect. The haemoglobin (Hb) variants of type Lepore are fusion proteins characterised by β-like globin chains with a δ-globin (HBD) N-terminus and a β-globin (HBB) C-terminus, whereas reciprocal products of underlying crossover events hold a HBB N-terminus and HBD C-terminus instead. Finally, Hb Parchman contains a β-like globin chain with a central HBB fragment and HBD-derived N-termini and C-termini, whereas reciprocal hybrid proteins are as yet unknown.

METHODS

The propositus was an 80-year-old Caucasian man, whose HbA1c quantification by HPLC (Variant II turbo) for exclusion of type-2 diabetes revealed an abnormal peak. Haemoglobins were analysed by ion-exchange HPLC (Variant II) and capillary electrophoresis (Sebia Capillarys Flex) and DNA by automatic Sanger sequencing of δ-globin and β-globin genes.

RESULTS

Sequencing showed an HBB-HBD-HBB hybrid gene, with HBD-derived central codons 9-31, and HBB-derived UTRs and complementary coding regions. The corresponding new hybrid haemoglobin (Hb Palencia) is represented at ≈40%, similar to HbA.

CONCLUSION

Hb Palencia contains the first globin variant with internal HBD sequences and HBB-derived N-terminal and C-terminal and regulatory sequences. Relative quantity of the new βδβ-type variant suggests transcriptional control by HBB elements and a half-life similar to normal HBB.

Thalassemia in the laboratory: pearls, pitfalls, and promises

Thalassemia is one of the most common hereditary disorders of the developing world, and it is associated with severe anemia and transfusion dependence. The global health burden of thalassemia has increased as a result of human mobility and migration in recent years. Depending on inherited mutations, thalassemia patients exhibit distorted hemoglobin (Hb) patterns and deviated red cell indices, both of which can be used to support identification by diagnostic tools. Diagnostic approaches vary depending on the target population and the aim of the testing. Current methods, which are based on Hb patterns, are used for first-line screening, whereas molecular testing is needed for conformation of the results and for prenatal and preimplantation genetic diagnosis. In the present paper, we review the diagnostic parameters, pitfalls, interfering factors, and methods; currently available best-practice guidelines; quality assurance and standardization of the procedures; and promising laboratory technologies for the future of thalassemia diagnosis.

Characterization of Two Deep Intronic Variants on the β-Globin Gene with Inconsistent Interpretations of Clinical Significance

Sequence variants located in the introns of the β-globin gene may affect the mRNA processing and cause β-thalassemia (β-thal). Sequence variants that change one of the invariant dinucleotides at the exon-intron boundaries may have fatal consequences for normal mRNA splicing. Intronic variants located far from obvious regulatory sequences can be more difficult to evaluate. There is a potential for misinterpretation of such sequence variants. Hence, thorough evaluation of patient data together with critical use of databases and in silico prediction tools are important. Here, we describe two rare sequence variants in the second intron of the β-globin gene, HBB: c.316-70C>G and HBB: c.316-125A>G (NM_000518.4), both previously reported as variants causing β-thal, and later as benign sequence variants. Due to the limited number of published cases and inconsistent interpretations, the significance of these sequence variants has been unclear. We have identified these two sequence variants in multiple individuals, alone and in a variety of combinations with other δ- and β-globin defects, and we find no influence of the sequence variants on the phenotype.