Nondeletional Α-thalassemia Research Articles

Detection of Hemoglobin Constant Spring: A Comparison of Capillary Electrophoresis Versus High-Performance Liquid Chromatography.

In Malaysia, Hemoglobin Constant Spring (Hb CS) is the most common non-deletional α-thalassemia, caused by a mutation at the termination codon of the α2-globin gene (TAA>CAA). Detection typically involves identifying an abnormal peak at zone 2 on capillary electrophoresis (CE) or a small peak at the C-window on high-performance liquid chromatography (HPLC), indicative of Hb CS. This study aimed to investigate the correlation between HPLC and CE in detecting Hb CS, evaluating their respective diagnostic accuracies and limitations. A cross-sectional study was conducted at Hospital Sultanah Nur Zahirah involving secondary school students (Form 4) from Terengganu who participated in a thalassemia screening program conducted by the Ministry of Health (MOH) from January 2019 to December 2022. Blood samples from subjects showing a positive peak in zone 2 of CE and a small peak at the C-window of HPLC were selected. Molecular studies of these samples were performed to confirm the presence of Hb CS. For the statistical analysis, the Pearson correlation coefficient was employed to assess the relationship between CEand HPLCresults. Hb CS was confirmed in all samples by molecular studies, revealing 92.3% heterozygous, 7.2% compound heterozygous, and 0.5% homozygous cases. CE detected 92.3% of heterozygous Hb CS cases, while HPLC detected only 48.2%. For compound heterozygous Hb CS, CE detected 100%, whereas HPLC detected 89.3%. Both homozygous cases were detected by CE and HPLC. The Pearson correlation coefficient test showed a significant linear relationship (p<0.001) between CE's zone 2 peak values and HPLC's C-window peaks (n=389). Conclusion: These findings highlight the efficacy of CE as a reliable method for Hb CS detection, suggesting its potential superiority over traditional HPLC in clinical settings.

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

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. 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. 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. 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.

LC-MS/MS-Based Absolute Quantitation of Hemoglobin Subunits from Dried Blood Spots Reveals Novel Biomarkers for α-Thalassemia Silent Carriers.

Identification of α-thalassemia silent carriers is challenging with conventional phenotype-based screening methods. A liquid chromatography tandem mass spectrometry (LC-MS/MS)-based approach may offer novel biomarkers to address this conundrum. In this study, we collected dried blood spot samples from individuals with three α-thalassemia subtypes for biomarker discovery and validation. We observed differential expression patterns of hemoglobin subunits among various α-thalassemia subtypes and normal controls through proteomic profiling of 51 samples in the discovery phase. Then, we developed and optimized a multiple reaction monitoring (MRM) assay to measure all detectable hemoglobin subunits. The validation phase was conducted in a cohort of 462 samples. Among the measured hemoglobin subunits, subunit μ was significantly upregulated in all the α-thalassemia groups with distinct fold changes. The hemoglobin subunit μ exhibits great potential as a novel biomarker for α-thalassemia, especially for silent α-thalassemia. We constructed predictive models based on the concentrations of hemoglobin subunits and their ratios to classify the various subtypes of α-thalassemia. In the binary classification problems of silent α-thalassemia vs normal, non-deletional α-thalassemia vs normal, and deletional α-thalassemia vs normal, the best performance of the models achieved average ROCAUCs of 0.9505, 0.9430, and 0.9976 in the cross-validation, respectively. In the multiclass model, the best performance achieved an average ROCAUC of 0.9290 in cross-validation. The performance of our MRM assay and models demonstrated that the hemoglobin subunit μ would play a vital role in screening silent α-thalassemia in clinical practice.

Fetal Hemoglobin H Hydrops Fetalis: Another Three Case Reports

We report three cases of fetalis hydrops associated with nondeletional α-thalassemia. Two cases were caused by hemoglobin (Hb) H-Quong Sz disease, and one caused by homozygous Hb Constant Spring. Fetal hydrops occurred in the late second trimester in all three cases. Our study indicates that for pregnancies at risk for fetal nondeletional Hb H disease, strict ultrasound follow-up is particularly important. Even without techniques of intrauterine transfusion treatment, early prenatal diagnosis can enable parents to make timely decisions.

Addison's disease in a lady with hemoglobin H disease

Hemoglobin H (HbH) disease is alpha (α)-thalassemia characterized by the inactivation of three of four α-globin genes due to deletions with or without nondeletional α-thalassemia. HbH disease is not necessarily a benign disorder as has been generally thought. Here, we report a 33-year-old female who has a lifelong history of anemia without blood transfusions. but when she got married, during pregnancies developed symptomatic moderate-to-severe anemia necessitating infrequent blood transfusions. Later due to symptomatic anemias and increasing the frequency of blood transfusions, she underwent splenectomy, 3 years from splenectomy she developed a gradual dark skin discoloration with frequent hypotension and was diagnosed with Addison's disease which is a rare endocrine complication of thalassemia-induced iron overload.

Analysis of Thalassemia Gene Carriers in 19 482 Pregnant Women from 2015 to 2019 in Guilin, Guangxi

To investigate the types and frequencies of thalassemia genes carried by the pregnant women in Guilin, Guangxi Zhuang Autonomous Region, China. From January 2015 to December 2019, blood samples of the pregnant women who visited the Outpatients of Obstetrics clinic and Eugenics Genetic clinic in Affiliated Hospital of Guilin Medical University were collected. Gap-PCR was used to detect deletional α-thalassemia, PCR-RDB to detect the gene mutations of non-deletional α-thalassemia and β-thalassemia, and MLPA or DNA sequencing to detect rare thalassemia mutations. Different types and frequencies of thalassemia mutations carried by pregnant women were analyzed statistically. A total of 19 482 blood samples were collected, including 3 801 thalassemia gene carriers (19.51%). Seven types of α-thalassemia gene mutation were detected with a carrier rate of 15.43%. Among them, --SEA deletion (7.32%), -α3.7 deletion (3.97%), and -α4.2 deletion (1.4%) were the commonest types. Twelve types of β-thalassemia mutations were detected with a carrier rate of 5.02%. Among them, CD41-42 (-TCTT) (2.32%), CD17 (AAG>TAG) (1.23%), and IVS-II-654 (C>T) (0.55%) were the commonest types. In addition, 107 cases of rare thalassemia gene mutations and abnormal hemoglobin were found at the same time. Guilin is a high-risk area for thalassemia. Alpha-thalassemia is dominated by --SEA deletion, -α3.7 deletion, and -α4.2 deletion, while β-thalassemia is by CD41-42 (-TCTT), CD17(AAG>TAG), and IVS-II-654(C>T).

Evaluation of intervention strategy of thalassemia for couples of childbearing ages in Centre of Southern China.

BackgroundTo describe the free intervention strategy of thalassemia for childbearing couples in Guangzhou.MethodsRoutine hematology examinations were conducted for 137,222 couples. Among them, 37,501 couples who had mean corpuscular volume (MCV) <82 fL or mean corpuscular hemoglobin <27 pg were elected for Hb analysis and the deletions of four common α‐thalassemia mutation. Reverse dot blot for common nondeletional α‐thalassemia and β‐thalassemia was selectively used. Three thousand twenty‐two couples randomly selected were offered all those tests as a control group. Sanger sequencing, multiplex ligation‐dependent probe amplification and next‐generation sequencing were used for rare thalassemia. High‐risk couples were offered prenatal diagnosis at 10–13 weeks’ gestation based on informed consent.ResultsThe carrier rates of α‐, β‐, and αβ‐thalassemia and δβ thalassemia/deletional HPFH were 7.7%, 3.02%, 0.5% and 0.059% respectively. Of them, 1.37% were identified as at‐risk couples and 345 couples terminated the pregnancy. No severe α‐ and β‐thalassemia births were observed. In the control group, two β‐ thalassemia carriers and one case with −α3.7/ααQS were misdiagnosed, but all at‐risk couples were found, and we could save 1,523,774 ¥ using our strategy. The cut‐off points of 73.46 fL and 23.25 pg would be useful to find −α+/αT thalassemia.ConclusionThe intervention strategy was cost‐effective and offered reference in population thalassemia screening.

Analysis of Gene Deficiency Types of Thalassemia in Lingui District of Guilin City

To analyze the gene defect types and distribution characteristics of α- and β-thalassemia in Lingui District of Guilin City, Guangxi, so as to provide scientific basis for genetic consultation and prevention measures. A total of 6 496 suspected cases for screening the thalassemia during physical examination, premarital examination, pregnancy examination and hospitalization in the Second Affiliated Hospital of Guilin Medical University from May 2016 to October 2019 were analyzed. Gap-PCR, PCR-RDB and DNA sequencing techniques were used to detect the types and constituent ratios of gene defects in α- and β-thalassemia positive cases. Among 6 496 suspected patients, 1 363 were thalassemia carriers, the total positive rate was 20.98%. There were 677 cases of single-gene deletion and 26 cases of double-gene detetion on the deletional α-thalassemia, 115 cases of non-deletion α-thalassemia mutation and 4 cases of deletion plus mutation. The positive rate of α-thalassemia was 12.66%. There were 11 gene abnormalities for α-thalassemia, of which --SEA/αα (50.36%) was the most common, followed by -α3.7/αα (23.84%); the main α-gene mutation was ααCS (6.93%). There were 514 β-thalassemia gene carriers, with a positive rate of 7.93%. In 12 types of β-gene mutations, CD41-42 (-TTCT) (55.64%) was the most common, followed by CD17 (A→T) (20.23%). There were 25 cases of double heterozygous α and β thalassemia (0.39%), of which -α3.7/βCD17 (24%) and --SEA/β41-42 (16%) were numerically dominant. Two of rare thalassemia genotypes were identified by sequencing, which were heterozygous mutations of Chinese Hong Kong type α thalassemia (HKαα/αα or HKαα/-α3.7) and β gene mutations IVS-I (-2) or codon30 (A→G) β0, respectively. Lingui district of Guilin city is a high incidence area of thalassemia. The mutation rate of α-thalassemia --SEA/αα type deletion is relatively high, followed by that of the right deletion type (-α3.7/αα). CD41-42 (-TTCT) has the highest mutation rate in β-thalassemia, followed by CD17(A→T). The results of this study provide reference data for the regional screening, diagnosis and treatment of thalassemia and eugenics.

Clinical Features of Pregnant Women with Thalassemia in Non Endemic Area

To investigate the clinical features of pregnant women with thalassemia in non endemic area, and to prevent the births of babies with intermedia or major thalassemia. Two hundred and thirty-five pregnants women with thalassemia diagnosed from March 2015 to April 2016 in our hospital were enrolled and retrospectively analysed. The blood routine and hemoglobin electrophoresis were performed respectively by XN-9000 automatic blood cell analyzer and HYDRASYS hemoglobin electrophoresis apparatus. The three commonest deletion of α-thalassemia, the three non-deletion α-thalassemia and 21 known β-thalassemia mutation were all detected by fluorescence melting curve analysis. Among 235 pregnant women of thalassemia, the majority were β-thalassemia, which were followed by α-thalassemia and composite thalassemia. Most pregnant women showed a mild anemia, and suffered from microcytic anemia, but less suffered from iron deficiency anemia. The ratio of second-child pregnant women was increased, and the ratio was close to one third both in α-thalassemia and β-thalassemia patients, and 75% patients were composite thalassemia. HbF was found to be more in native pregnant women with β-thalassemia. Hemoglobin isomer was easy to found in the pregnant with α-thalassemia, and they were all non native. The genotype of --sea were found majority in both native and non native pregnant women with thalassemia. The genotype of IVS-II-654 made up a large majority(55.38%) in native pregnant with β-thalassemia, as well as one of whose parents was native pregnant women. The genotypes of CD41-42,IVS-II-654 and CD17 were found to be a large majority in non native pregnant women, each of them accounted for 30%. More pregnant women with thalassemia are founded to be in non endemic area, and shows their own unique clinical features. It is certainly to detect thalassemia mutation in their spouse and their babies, to prevent the births of babies with intermedia or major thalassemia.

First report of the spectrum of δ-globin gene mutations among women of reproductive age in Fujian area-Discrimination of δ-thalassemia, α-thalassemia, and Iron Deficiency Anemia.

BackgroundLow HbA2 level is an underlying of δ‐thalassemia, α‐thalassemia, and IDA. Interactions of these disorders can generate a wide spectrum of phenotype, which will pose diagnostic conundrum for clinical assessment, carrier screening, and genetic counseling.MethodsSubjects with HbA2 levels below 2.0% with normal or reduced hematological parameters were recruited for further investigation. δ‐globin gene mutations were identified by DNA sequencing of the HBD gene. Serum ferritin (SF) concentration was determined by the chemiluminescent microparticle immunoassay. The three common deletional α‐thalassemia (‐‐SEA/αα, ‐α3.7/αα, and ‐α4.2/αα) were detected using Gap‐PCR, detection of the point mutations in the three nondeletional α‐thalassemia (αCSα/αα,αQSα/αα,αWSα/αα), and the 17 common β‐thalassemia was performed using reverse dot blot hybridization (RDB).ResultsWe had characterized the δ‐globin gene mutations in 20 cases, revealing a frequency of 0.4% in the women of reproductive age (20/4 792). Two previously known mutations:‐77 T > C and −30 T > C and 3 novel δ‐globin gene defects: −44G > A,CD87C > T, and CD134T > A were found. In the selected cases, we also found 85 cases confirmed with (51.2%,85/166) IDA and 39 cases (23.5%,39/166) with common α‐thalassemia. Subjects with δ‐thalassemia had statistically higher levels of Hb, MCV, and MCH compared with other two groups, whereas statistically lower levels of RDW were seen in δ‐thalassemia group. What's more, statistically higher levels of SF were seen in δ‐thalassemia group, compared with IDA groups.ConclusionWe reported the spectrum of δ‐thalassemia mutations for the first time with the frequency of 0.4% among women of reproductive age in Fujian area and found that −77T > C mutation was the most common mutation, followed by −30T > C mutation. What's more, 3 novel δ‐globin gene defects: −44G > A,CD87C > T and CD134T > A were found. A thorough analysis of the hematological, electrophoretic characterization, and the level of SF was needed to suspect and further investigate the existence of IDA, α‐thalassemia, and δ‐thalassemia.

A Nested Asymmetric PCR Melting Curve Assay for One-Step Genotyping of Nondeletional α-Thalassemia Mutations

A rapid DNA-based assay is essential for clinical diagnosis and mass screening in thalassemia-prevention programs. Because of high homology and guanine-cytosine-rich and complex second structure of α-globin genes, it is rather difficult to develop a feasible and simple method for α-thalassemia genotyping. In this study, a strategy of nested asymmetric PCR melting curve analysis was designed to tackle these factors and ensure sensitivity and accuracy. Herein, a novel one-step assay for genotyping of nondeletional α-thalassemia mutations, including hemoglobin (Hb) Westmead (HBA2: c.369C>G), Hb Quong Sze (HBA2: c.377T>C), Hb Constant Spring (HBA2: c.427T>C), CD30 (HBA2: c.91-93delGAG), and CD31 (HBA2: c.95G>A) in a single closed tube, was established and evaluated. All five mutations were accurately determined with the concordance rate of 100% in a blind analysis of 255 genotype-known samples and 1250 clinical samples. In conclusion, this assay is useful for rapid and reliable genotyping of nondeletional α-thalassemia mutations in clinical practice. Especially, the strategy may have the potential to be a versatile scheme for rapid genotyping of other gene mutations because of its high throughput, sufficient stability, low cost, and simple operation.

Characterization of deletional and non-deletional alpha globin variants in a large cohort from Spain between 2009 and 2014.

The hemoglobinopathies are a group of disorders passed down through families (inherited) in which there is abnormal production or structure of the hemoglobin molecule. They are among the most common inherited diseases around the world. Those that produce abnormal hemoglobin are called structural hemoglobinopathies while thalassemia is another type of disorder that is caused by a defect in the gene production of the globin chains. In a study ambispective comprising 1623 patients, 153 subjects showed an abnormal hemoglobin and 1470 with hypochromic and microcytic anemia, and of these 1470, 23 patients were studied for simultaneously α-thalassemias and structural hemoglobinopathies. Among the α-thalassaemia cases, 1282 cases (87.2%) were deletional α-thalassemia, 172 cases (11.7%) were non-deletional α-thalassemia, and 16 cases (1.1%) were deletional and non-deletional α-thalassamias simultaneously. Thus, approximately 12% of the cases were non-deletional α-thalassaemia. Clinical diagnosis, only 19 severe cases (1 hydrops fetalis and 18 instances of Hb H disease), 1200 thalassamias traits, and 160 thalassaemia silent carriers were recorded within the α-thalassaemia. Regarding structural hemoglobinopathies, there were only 2 cases of hemoglobinopathies with low oxygen affinity and 1 case of hemoglobin M; the remaining 150 were silent hemoglobinopathies. Non-deletional α-thalassaemia represented 12% of all α-thalassemias in our region; the most common deletion in our area was the 3.7-kb deletions, followed by Asian --(SEA) and --(FIL). The alterations responsible for non-deletional α-thalassaemia are most represented by the Hph and Hb Groene Hart and, in the case of structural hemoglobinopathies, Hb Le Lamentin and Hb J-Paris.

Variant analysis for patients from Fujian area with Hong Kong αα type thalassemia

To determine the frequency of Hong Kong αα (HK αα) gene in α3.7 positive samples among carriers from Fujian area. Routine genetic testing for thalassemia was carried out for 10145 patients with positive screening results. Single PCR and two-round nested PCR were utilized to detect HK αα among 507 patients with α3.7/αα and 2 patients for whom electrophoresis showed α3.7, -αSEA and normal α2 alleles. Reverse dot blot test was used for detecting non-deletional α-thalassemia and β-thalassemia variants. Among the 507 patients with α3.7/αα, HK αα was identified in 35 cases, which included 25 HK αα/αα, 5 HK αα/α3.7, 4 HK αα/αα with heterozygous CD41/42 (HBB: c.126_129delCTTT) variant, 1 HK αα/αα with IVS-II-654 (HBB: c.316_197C>T) heterozygous variant. One patient was confirmed to have α3.7/anti4.2 genotype. The two cases with α3.7, -αSEA and normal α2 alleles were confirmed to be HK αα/--SEA. The frequency of HK αα genotype in Fujian area was therefore 7.27% among patients with α3.7 and 0.36% in the general population. A certain proportion of HK αα has been detected in Fujian area, which will enable more accurate diagnosis and genetic counseling.

Derivation of the human induced pluripotent stem cell line MUi017-A from a patient with homozygous Hemoglobin Constant Spring

Hemoglobin Constant Spring (HbCS, HBA2: c.427T>C) is a common nondeletional α-thalassemia resulting from a nucleotide substitution at the termination codon of the HBA2 gene. Homozygosity for HbCS is characterized with mild anemia, jaundice, and splenomegaly. In this study, the human induced pluripotent stem cell line MUi017-A was successfully generated from peripheral blood CD34+ hematopoietic progenitors of a 52year old female with homozygous HbCS. The MUi017-A cell line exhibited embryonic stem cell characteristics with consistent expression of specific pluripotency markers and the capability of differentiating into the three germ layers. The cell line may be used for the disease modeling.

Molecular Study of Deletional and Nondeletional Mutations on the α-Globin Locus in the Azeri Population of Northwestern Iran

The aim of this study was to determine the molecular spectrum and frequency of deletional and nondeletional α-thalassemia (α-thal) mutations and the genotype–phenotype correlation in common mutations in the Azeri population of Northwestern Iran. A total of 1256 potential carriers with microcytic and hypochromic anemia and normal Hb A2 levels (<3.5%) and without iron deficiency anemia plus three fetuses were identified. Multiplex gap-polymerase chain reaction (gap-PCR) and sequencing for α-thal mutations were carried out. In 606 individuals, the α-globin gene was normal, but in 650 persons (51.6%) and three fetuses, 10 different mutations were detected. The most frequent deletional genotypes were as follows: αα/–α3.7 (61.7%), –α3.7/–α3.7 (11.9%), αα/–α4.2 (4.6%), αα/– –MED (4.3%) and αα/–(α)20.5 (3.8%). The most frequent nondeletional genotypes were αα/αIVS-I (–5 nt)α (HBA2: c.95+2_95+6delTGAGG) and αα/αPoly A2α [polyadenylation signal (polyA2) (AATAAA>AATGAA); HBA2: c.*96G>A] with frequencies of 1.08% and 0.92%, respectively. Meanwhile, 7.71% of individuals with a proven β-thalassemia (β-thal) mutation were found to also carry an α-thal mutation. Persons having two functional α-globin genes showed lower mean corpuscular volume (MCV) and mean corpuscular hemoglobin (Hb) (MCH) values compared to those with one mutated α-globin gene, provided that they had normal β-globin genes. Overall, the incidence of α-thal was 2.7% in the Azeri population in Northwestern Iran. Our results showed that the variability of α-thal mutations are high in the Azeri population and that α-thal mutations are highly heterogeneous in both deletional and nondeletional genotype aspects.

Hydrops Fetalis Associated with Compound Heterozygosity for Hb Zurich-Albisrieden (HBA2: C.178G > C) and the Southeast Asian (– –SEA/) Deletion

Hb Zurich-Albisrieden [HBA2: c.178G > C; α59(E8)Gly→Arg (α2)] is a rare nondeletional α-thalassemia (α-thal) that results from a nucleotide substitution at codon 59 of the α2-globin gene. In this report, we present a fetus with cardiomegaly, enlarged placenta and increased middle cerebral artery-peak systolic velocity (MCA-PSV) at 25 weeks’ gestation. Fetal blood sampling revealed the severe anemia [hemoglobin (Hb) level being 5.5 g/dL] and Hb H (β4) disease-like hematological findings with Hb Bart’s (γ4) level of 30.7%. Molecular analysis of the family found that the father was an Hb Zurich-Albisrieden carrier, the mother heterozygous for the – –SEA α0-thal deletion, and the fetus was a compound heterozygote for Hb Zurich-Albisrieden and the – –SEA α0-thal deletion. Therefore, this was a rare case of Hb Bart’s hydrops fetalis associated with Hb Zurich Albisrieden.

First Case of a Compound Heterozygosity for Two Nondeletional α-Thalassemia mutations, Hb Constant Spring and Hb Quong Sze

Nondeletional α-thalassemia (α-thal) is the result of point mutations in critical regions of the α-globin genes, affecting mRNA processing, mRNA translation, or α-globin stability. Hb Constant Spring (Hb CS, HBA2: c.427T > C) is the most common nondeletional α-thal that results from a nucleotide substitution at the termination codon of the α2-globin gene. Hb Quong Sze (Hb QS, HBA2: c.377T > C) is another nondeletional α-thal in South China with the missense mutation at codon 125 of the α2-globin gene making this hemoglobin (Hb) variant highly unstable. Although homozygosity for Hb CS (αCSα/αCSα) or Hb QS (αQSα/αQSα) has been reported, clinical pictures vary from severe hemolysis that developed early in life to only mild anemia, no clinical phenotypic data of compound heterozygosity for Hb CS/Hb QS (αCSα/αQSα) has been described. In this report we describe an adult case with such a compound heterozygosity who presented with a mild α-thal.

Fetal Anemia and Hydrops Fetalis Associated with Homozygous Hb Constant Spring (HBA2: c.427T > C)

Hb Constant Spring (Hb CS, HBA2: c.427T > C) is a common nondeletional α-thalassemia (α-thal) that results from a nucleotide substitution at the termination codon of the α2-globin gene. Homozygosity for Hb CS (αCSα/αCSα) is relatively rare, and generally characterized with mild hemolytic anemia, jaundice, and splenomegaly. In this report we present a fetus with cardiomegaly, pericardial effusion, enlarged placenta and increased middle cerebral artery-peak systolic velocity (MCA-PSV) at 24 weeks’ gestation. Fetal blood sampling revealed the severe anemia [hemoglobin (Hb) level being 4.8 g/dL] and Hb H (β4) disease-like hematological findings with Hb Bart’s (γ4) level of 17.9%. DNA sequencing of the α-globin genes found that both partners were Hb CS carriers and the fetus was an Hb CS homozygote. Therefore, this was a rare case of homozygous Hb CS which demonstrated an unusual and serious anemia and hydrops fetalis in utero.

Analysis of α1 and α2 globin genes among patients with hemoglobin Adana in Malaysia.

Hemoglobin (Hb) Adana [HBA2: c179G>A (or HBA1); p.Gly60Asp] is a non-deletional α-thalassemia variant found in Malaysia. An improvement in the molecular techniques in recent years has made identification of Hb Adana much easier. For this study, a total of 26 Hb Adana α-thalassemia intermedia and 10 Hb Adana trait blood samples were collected from patients. Common deletional and non-deletional α-thalassemia genotypes were determined using multiplex gap polymerase chain reaction (PCR) and multiplex ARMS PCR techniques. Identification of the Hb Adana location on the α-globin gene was carried out using genomic sequencing and the location of the mutation was confirmed via restriction fragment length polymorphism-PCR. Among the 36 samples, 24 (66.7%) had the -α(3.7)/α(Cd59)α mutation, while the -α(3.7)/α(Cd59)α mutation accounted for 2 samples (5.6%) and the remaining 10 (27.8%) samples were α/α(Cd59)α. All 36 samples were found to have the Hb Adana mutation on the α2-globin gene. The position of the α-globin gene mutation found in our cases was similar to that reported in Indonesia (16%) but not to that in Turkey (0.6%). Our results showed that the Hb Adana mutation was preferentially present in the α2-globin genes in Malays compared to the other ethnicities in Malaysia. Thus, the Malays might have similar ancestry based on the similarities in the Hb Adana position.

Identification of Nondeletional α-Thalassemia in a Prenatal Screening Program by Reverse Dot-Blot in Southern China

The aim of this study was to demonstrate the performance of nondeletional α-thalassemia (α-thal) prevention using a reverse dot-blot method at a Mainland Chinese hospital. A prenatal control program for nondeletional Hb H disease was performed between January 2009 and December 2013. All couples were screened for α-thal trait, and for couples in which one partner tested positive for α0-thal, the other was subjected to screening for Hb Constant Spring (Hb CS, HBA2: c.427T > C) and Hb Quong Sze (Hb QS, HBA2: c.377T > C) mutations by reverse dot-blot assay. Prenatal diagnoses were offered in at-risk pregnancies. During the study period, 51,105 couples were found to be carrying α-thal; among these, 35 (0.07%) couples were found to be at-risk of conceiving an offspring with nondeletional Hb H disease, including 25 couples for Hb H-CS and 10 cases for Hb H-QS. Nine fetuses were diagnosed with nondeletional Hb H disease, and eight of the affected pregnancies were terminated. Detection of nondeletional α-thal is necessary for any prenatal diagnosis (PND) programs in Southeast Asian countries. Reverse dot-blot is a relatively simple method for simultaneous typing of common nondeletional α-thal mutations.