Bart's Hydrops Research Articles

The Clinical Severity of Alpha-2 Globin Gene Variants: Homozygosity for Hb Agrinio (HBA2: c.89T>C) Leads to Severe Antenatal Anemia, about 8 Cases in 3 Families

Introduction: Hemoglobin (Hb) Agrinio (HBA2: c.89T>C (Leu29Pro) mutation) is a rare highly unstable Hb variant resulting from a leucine to proline substitution at codon29 of the alpha2-globin gene. Eleven homozygous cases of this non-deletional alpha thalassemia were described in literature. Clinical course ranged from moderate (non-transfusion dependent anemia) to severe (transfusion dependent thalassemia). In addition, one probable case of Hb barts hydrops fetalis was also reported in a Greek series. Hb Agrinio was first described in individuals of Greek or Cypriot origins. Subsequently, some cases were reported among patients living in Spain and Macedonia, most often of Gypsy origin. We report here the clinical presentation of the 8 homozygous cases diagnosed by molecular biology analysis in France and underline the severity of the antenatal phenotype of the disease. Methods: Cases were identified by contacting all the French laboratories involved in the molecular diagnosis of hereditary red blood cell (RBC) disorders. Three different families were retrieved, including 8 pediatric homozygous cases diagnosed by alpha globin gene sequencing between 2006 and 2020. Standardized clinical and laboratory data were obtained from treatment centers. All parents gave their written consent for molecular analysis and their authorization for participating in this study. Results: Consanguinity was present in all 3 families, however no obvious link was found between the 3. Two originated from Spain (1 of gypsy origin) and 1 from Bulgaria. All patients were homozygous for the HBA2: c.89T>C mutation, without any additional beta or alpha anomalies using gene sequencing and MLPA. Main clinical presentation findings of homozygous patients are reported in the table. Among the 8 cases, there was one in utero death at 22 weeks GA and 7 living births. Three patients, the more anemic at birth, died during the first hours of life with a clinical picture of hydrops fetalis for 2 of them. Despite a normal cerebral doppler at 32 weeks of GA, the third newborn (II2), presented at birth with a blueberry syndrome with cutaneous and hepatic extramedullary hematopoiesis, severe pulmonary arterial hypertension and Hb value of 6 g/dl, leading to neonatal death. Among the 4 survivor patients, one (III3), diagnosed in the antenatal period, benefited from in utero transfusions (TF) administered at 23 and 27 weeks because an accelerated middle cerebral artery peak systolic velocity of 52cm/s was measured. Hypospadias with ambiguous genitalia requiring surgical treatment was present in one patient and micropenis treated medically and undescended testis in a second one. All survivors (n=4/8) are currently under regular TF and chelation therapy. TF were generally (3/4) occasional in the first years of life and then became regular (>8 TF/year) later in childhood (at 6, 6, 7 years of age respectively). Conclusions: our national experience of homozygous Hb Agrinio cases revealed a more severe clinical course than reported in literature, with clinical presentation ranging from alpha-thalassemia major (Hb Barts hydrops fetalis) to severe non deletional HbH disease. Antenatal anemia was profound. In utero or neonatal deaths concerned half of the patients and additional ones were, even not biologically confirmed, also found in the family histories. Of note, congenital urogenital abnormalities similar to those found in the classical Hb Bart's Hydrops FetalisSyndrome were found in 2 patients. This up to now unreported severity could be explained by a closer monitoring and a more comprehensive clinical study of the cases/siblings allowing the antenatal period to be better described. The existence of aggravating genetic factor is another hypothesis and NGS analysis of genes involved in RBC disorders is planned. In couples at risk for homozygous Hb Agrinio, early genetic counseling and prenatal diagnosis should be offered. If the pregnancy is continued, a very close fetal ultrasound monitoring is mandatory and intrauterine TFs can be administered when severe fetal anemia is detected. Table Disclosures Thuret: Celgene: Membership on an entity's Board of Directors or advisory committees, Other: Investigator in clinical trials; Novartis pharma: Membership on an entity's Board of Directors or advisory committees, Other: Investigator in clinical trials; bluebird bio, Inc.: Membership on an entity's Board of Directors or advisory committees, Other: Investigator in clinical trials; Apopharma: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Alpha thalassemia genotypes in Kuwait

BackgroundThe frequency of the alpha thalassemia trait is approximately 40% in the Kuwaiti population, but there has been no comprehensive study of the prevalent alleles. This is a report of patients who were referred for molecular diagnosis over a 20-year period.MethodsThis is a retrospective study of the α-globin genotypes obtained in the Hemoglobin Research Laboratory of the Department of Pediatrics, Kuwait University from 1994 to 2015. Genotyping was performed by a combination of PCR, allele-specific oligonucleotide hybridization and reverse dot blot hybridization (Vienna Lab Strip Assay).ResultsFour hundred samples were characterized and analyzed from individuals aged < 1 month to 80 years, with a median of 6 years from 283 unrelated families. Most (90.8%) were Kuwaiti nationals. The commonest genotype was homozygosity for the polyadenylation-1 mutation (αPA-1α/α PA-1α) in 33.3% of the samples, followed by heterozygosity (αα/α PA-1α) for the same mutation in 32.3%. PA-1 was therefore the most frequent allele (0.59). The frequency of the α0 (−-MED) allele was 0.017. Rare alleles that were found in very low frequencies included α0 (−-FIL) in a Filipino child, Hb Constant Spring, Hb Adana, and Hb Icaria.ConclusionThere is a wide variety of alpha thalassemia alleles among Kuwaitis, but nondeletional PA-1 is by far the most common cause of the moderate to severe HbH (β4 tetramer) disease phenotype. The α0 (−MED) allele is also encountered, which has implications for premarital counseling, especially for the possibility of having babies with alpha thalassemia major (Barts hydrops fetalis).

Noninvasive Prenatal Detection of Hemoglobin Bart Hydrops Fetalis Via Maternal Plasma Dispensed With Parental Haplotyping Using the Semiconductor Sequencing Platform

(Abstracted from Am J Obstet Gynecol 2020;222:185.e1–185.e17) Hemoglobin Bart's hydrops fetalis syndrome (Hb Bart's) is a common inherited genetic disease in the south of China and Southeast Asia. Couples who are both carriers of the Southeast Asian type of α-thalassemia gene deletion have a 25% risk of having a pregnancy affected with Hb Bart's as a result of autosomal recessive inheritance.

Clinical practice guidelines for alpha-thalassemia

Alpha-thalassemia is an autosomal recessive genetic disease as well as a relatively common hemoglobinopathy. Severe alpha-thalassemia (also known as Hb Bart's Hydrops fetalis syndrome) and intermediate alpha-thalassemia (also known as Hb H disease) are among the most common birth defects in southern China. To implement carrier screening and large population prevention program in high incidence areas can significantly reduce the incidence of alpha-thalassemia. This guideline was established by combining the discoveries of basic research, clinical research and guidelines from other countries and the actual data of Chinese population. It has summarized the medical genetics knowledge and key points in the clinical treatment for alpha-thalassemia, and provided suggestions for the clinical diagnosis and standard management of patients.

Diagnosis of patients with hemoglobinopathies including α-thalassemia in a laboratory with limited resources

BACKGROUND: Diagnosis of α-thalassemia can be challenging as it is clinically insignificant in the majority of patients who are presented with one or two α-gene deletion, it cannot be always suspected from the red cell indices, and the confirmatory tests of α-thalassemia are not readily available, applied, and/or provide conclusive results. The importance of diagnosis of α-thalassemia is mainly to identify the patients with α0-thalassemia, hemoglobin (Hb) H disease, Hb Bart's hydrops fetalis, and to identify the ameliorating effect that the coinheritance of α-thalassemia may have on the clinical phenotype of patients with HbS and other structural β-globin chain variants and/or patients with beta-thalassemia. The aim of this study is to evaluate the presentation and diagnosis of patients with α-thalassemia in a cohort of Iraqi patients with hemoglobinopathies.PATIENTS, MATERIALS, AND METHODS: This is a prospective cohort study that included 216 patients diagnosed with different types of hemoglobinopathies from June 2016 to October 2019. For each patient after reviewing the cause of presentation and family history of thalassemia, blood samples were sent for complete blood count, including calculated absolute reticulocyte count, peripheral blood smear, Hb H preparation, serum iron and total iron-binding capacity, sickling test, and if indicated Hb high-performance liquid chromatography (HPLC) (using BioRad D10). Family study was requested for several patients.RESULTS: Male:female for patients with α-thalassemia is 1:1.25. Consanguinity and family history of α-thalassemia are present in 85.2% and 51.9%, respectively. Out of 216 patients with different types of hemoglobinopathies, 25% are diagnosed with isolated or copresence of α-thalassemia. Low/lower normal HbA2% is the most sensitive parameter for the diagnosis of α-thalassemia.CONCLUSIONS: The most sensitive parameter for the diagnosis of α-thalassemia in this study is the low/lower normal HbA2% in patient with normal iron study. Other parameters such as the presence of golf-ball red cells in Hb H preparation and/or presence of HbH wave in Hb HPLC can be helpful but are only seen in smaller fraction of patients.

Noninvasive prenatal detection of hemoglobin Bart hydrops fetalis via maternal plasma dispensed with parental haplotyping using the semiconductor sequencing platform

Thalassemia is one of the most common monogenetic diseases in the south of China and Southeast Asia. Hemoglobin Bart's hydrops fetalis syndrome was caused by a homozygous Southeast Asian deletion (-/-) in the HBA gene. Few studies have proved the potential of screen for Bart's hydrops fetalis using fetal cell-free DNA. However, the number of cases is still relatively small. Clinical trials of large samples would be needed. In this study, we aimed to develop a noninvasive method of target-captured sequencing and genotyping by the Bayesian method using cell-free fetal DNA to identify the fetal genotype in pregnant women who are at risk of having hemoglobin Bart hydrops fetalis in a large-scale study. In total, 192,173 couples from 30 hospitals were enrolled in our study and 878 couples were recruited, among whom both the pregnant women and their husbands were detected to be carriers of Southeast Asian type (-/αα) of α-thalassemia. Prenatal diagnosis was performed by chorionic villus sampling, amniocentesis, or cordocentesis using gap-polymerase chain reaction considered as the golden standard. As a result, we found that the sensitivity and specificity of our noninvasive method were 98.81% and 94.72%, respectively, in the training set as well as 100% and 99.31%, respectively, in the testing set. Moreover, our method could identify all of 885 maternal samples with the Southeast Asian carrier and 36 trisomy samples with 100% of sensitivity in T13, T18, and T21 and 99.89% (1 of 917) and 99.88% (1 of 888) of specificity in T18 and T21, respectively. Our method opens the possibility of early screening for maternal genotyping of α-thalassemia, fetal aneuploidies in chromosomes 13/18/21, and hemoglobin Bart hydrops fetalis detection in 1 tube of maternal plasma.

Molecular characteristics of thalassemia and hemoglobin variants in prenatal diagnosis program in northern Thailand.

Molecular analysis of globin genes is an essential process for prenatal diagnosis (PND) of severe thalassemia. This study aimed to describe the molecular characteristics of thalassemia and hemoglobin (Hb) variants in PND program in northern Thailand. The type and frequency of globin gene mutations from 1290 couples at risk of fetal severe thalassemia diseases that were tested at Thalassemia Laboratory at Chiang Mai University from 2012 to 2017 were retrospectively reviewed. The PND program detected 444 (34.4%), 196 (15.2%) and 642 (49.8%) couples at risk of fetal Hb Bart's hydrops fetalis, beta-thalassemia major (BTM) and beta-thalassemia/Hb E disease, respectively. Coinheritance of more than one type of thalassemia was common and eight (0.6%) couples were at risk of two types of severe thalassemia. There were two types of alpha0-thalassemia; 893 (99.7%) Southeast Asian and 3 (0.3%) Thai deletions. Twenty beta-globin gene mutations were found with 94.3% of beta0-thalassemia. The codon 41/42 (- TTCT), codon 17 (A>T), IVS-I-1 (G>T) and codon 71/72 (+ A) comprised 90% of beta-thalassemia mutations. The study shows a high percentage of couples at risk of fetal Hb Bart's hydrops fetalis and BTM. The percentage of beta0-thalassemia is higher than those seen in other regions of Thailand.

The comparison of two whole genome amplification methods: A new method of pre-implantation genetic testing (PGT-M) for Southeast Asian deletion in alpha-thalassemia using high resolution melting analysis

Introduction In Southeast Asia, alpha-thalassemia with Southeast Asian (SEA) deletion type is the most common mutations of alpha-thalassemia-1 which can cause severe form known as Bart's hydrops fetalis. For couples which carrier of single gene defects, pre-implantation genetic testing for monogenic (PGT-M) plays a role in genetic testing for selecting of unaffected embryos prior implantation. Recently, high resolution melting (HRM) analysis is a simple, rapid and widely used for genotyping and gene scanning of genetic variation. In this study, we developed HRM analysis method for detection of SEA deletion in alpha-thalassemia and compared two WGA methods, SurePlex DNA Amplification System and REPLI-g Single Cell on the performance of HRM analysis and linkage analysis. Material and Methods Retrospective study was carried out in a single private fertility clinic from 2015 to 2017. The single cell embryos were biopsied on blastocyst stage from couples with disease- carrier of SEA deletion type. The trophectoderm biopsied cells were amplified by two whole genome amplification (WGA), SurePlex DNA Amplification System-PCR based method (Illumina, USA) and REPLI-g MDA Single Cell (QIAGEN, Germany). All WGA products were analyzed with two primer pairs of HRM analysis for detection of SEA deletion type in alpha-thalassemia disease and confirmed with the informative short tandem repeated (STRs) linkage analysis. Results A total of 53 single cell biopsied were amplified with SurePlex-WGA (n=33) and REPLI-g MDA (n=20) which used as template for HRM analysis. The HRM results revealed clearly distinguished between wild type and mutant type of SEA deletion mutation in alpha-thalassemia. Comparing between two WGA methods, the HRM amplification results efficiency and allele drop out (ADO) rate of REPLI- g MDA were 95% (19/20) and 31.57% (6/19), respectively. Meanwhile, for SurePlex-WGA showed 75.76% (25/33) and 28% (7/25), respectively. Furthermore, the HRM melting profile results of REPLI-g MDA showed higher concordance rate with the informative STRs linkage analysis results (63.16%, 12/18) than that of SurePlex-WGA (48%, 12/25). Conclusions HRM analysis is an alternative technique with high sensitivity and accuracy for detecting of alpha-thalassemia mutations. The REPLI-g MDA Single Cell method with HRM analysis is suitable for detection of alpha-thalassemia1 SEA type deletion in PGT-M and provided a good concordance with informative STRs linkage analysis. However, ADO from PCR amplification could be occurred and caused of misdiagnosis which might be affected to the interpretation results of the embryos disease- status. Thus, the mutation analysis method using HRM analysis combined with STRs linkage analysis are recommend in PGT-M to avoid the effected of ADO and increase the accuracy and reliable of the PGT-M results.

Invasive molecular prenatal diagnosis of alpha and beta thalassemia among Hakka pregnant women.

This study is a retrospective analysis of the prenatal genetic diagnosis results of fetuses with high risk of major thalassemia to provide information for clinical genetic counseling and to better control the birth of major thalassemia child in Hakka population. Totally, 467 fetuses in at-risk pregnancies were collected from Meizhou people's hospital from January 2014 to December 2017. Genomic DNAs were extracted from peripheral blood of the couples and villus, amniotic fluid or cord blood of the fetuses. DNA-based diagnosis was performed using polymerase chain reaction (PCR) and flow-through hybridization technique. Follow-up visits were done half a year after the fetuses were born. Around 467 fetus at-risk pregnancies were performed prenatal diagnosis. We detected 88 CVS samples, 375 amniocentesis fluid samples and, 4 cord blood samples. The 356 fetuses in α-thalassemia families consisted of 69 (19.38%) with Bart's hydrops syndrome, 20 (5.62%) fetuses with Hb H disease, and 184 (51.68%) fetuses with heterozygote. And the 111 fetuses in β-thalassemia families consisted of 31 (27.93%) thalassemia major, 51 (45.95%) fetuses with heterozygote. There are 13 fetuses with α+β-thalassemia, including 2 cases with severe β-thalassemia. DNA-based testing prenatal diagnosis of thalassemia was found to be highly reliable. Our findings provide key information for clinical genetic counseling of prenatal diagnosis for major thalassemia in Hakka pregnant women. Our work plays an important role in the prevention and control of thalassemia in Hakka population. We will also combine other techniques to further improve our molecular prenatal diagnostic capabilities, including the next-generation sequencing (NGS), Sanger sequencing and MLPA.

Potential new approaches to the management of the Hb Bart's hydrops fetalis syndrome: the most severe form of α-thalassemia.

The α-thalassemia trait, associated with deletions removing both α-globin genes from 1 chromosome (genotype ζ αα/ζ--), is common throughout Southeast Asia. Consequently, many pregnancies in couples of Southeast Asian origin carry a 1 in 4 risk of producing a fetus inheriting no functional α-globin genes (ζ--/ζ--), leading to hemoglobin (Hb) Bart's hydrops fetalis syndrome (BHFS). Expression of the embryonic α-globin genes (ζ-globin) is normally limited to the early stages of primitive erythropoiesis, and so when the ζ-globin genes are silenced, at ∼6 weeks of gestation, there should be no α-like globin chains to pair with the fetal γ-globin chains of Hb, which consequently form nonfunctional tetramers (γ4) known as Hb Bart's. When deletions leave the ζ-globin gene intact, a low level of ζ-globin gene expression continues in definitive erythroid cells, producing small amounts of Hb Portland (ζ2γ2), a functional form of Hb that allows the fetus to survive up to the second or third trimester. Untreated, all affected individuals die at these stages of development. Prevention is therefore of paramount importance. With improvements in early diagnosis, intrauterine transfusion, and advanced perinatal care, there are now a small number of individuals with BHFS who have survived, with variable outcomes. A deeper understanding of the mechanism underlying the switch from ζ- to α-globin expression could enable persistence or reactivation of embryonic globin synthesis in definitive cells, thereby providing new therapeutic options for such patients.

Molecular analysis of hemoglobinopathies in a large ethnic Hakka population in southern China.

Thalassemia is an inherited autosomal recessive disorder with microcytic hypochromic anemia resulting from reduced or absent synthesis of 1 or more of the globin chains of hemoglobin. This study provided the insight into prevalence and molecular characterization of thalassemia in Hakka population. 14,524 unrelated subjects were included in our study from January 2015 to November 2017. All the subjects were detected by hematological analysis, hemoglobin electrophoresis analysis, and molecular diagnosis (gap-polymerase chain reaction and flow-through hybridization technology). Data analysis was used to compare allele frequencies between the Hakka populations. Seven thousand four hundred twenty-two cases of microcytosis were found. The percentage of microcytosis in Meizhou, Ganzhou, and Heyuan was 50.91% (6738/13,236), 51.27% (445/868), and 56.90% (239/420), respectively. A total of 5516 mutant chromosomes were identified, including 3775 α-thalassemia and 1741 β-thalassemia. --SEA/αα was the most common α-thalassemia genotype, followed by -α3.7/αα and -α4.2/αα, accounted for 84.92% of α-thalassemia genotypes. Twelve kinds of mutations and 26 genotypes in β-thalassemia were found. IVS-II-654(C→T), CD41-42(-TCTT), −28(A→G), and CD17(A→T) alleles accounted for 92.65% of these mutations. IVS-II-654/N, CD41-42/N, -28/N, CD17/N genotypes accounted for 91.53% of β-thalassemia genotypes. 27 fetuses with at-risk pregnancies were subjected to prenatal diagnosis. Five fetuses were Bart's hydrops syndrome and 2 fetuses with β-thalassemia major. There were some differences in molecular characterization of thalassemia among Hakka people in different areas of southern China. Our results enriched the related information of thalassemia in the region, which provided valuable references for the prevention and control of thalassemia.

Molecular characterization of Hb H disease in southern Thailand.

Genotypes of 260 individuals with hemoglobin H (Hb H) disease originating from various provinces in southern Thailand were characterized by multiplex PCR (M-PCR) and reverse dot blot hybridization (RDB). M-PCR was used to amplify target fragments and then hybridized with allele-specific oligonucleotide (ASO) probes which were bound on a nylon membrane. A total of eight α-thalassemia (α-thal) mutations, which produced eight Hb H disease genotypes (α0-thal/α+-thal), were detected. The most common form of α0-thal was -SEA with a frequency of 99.23%. The other form (0.77%) of α0-thal mutation was a THAI deletion (-THAI). The deletional α+-thal mutations comprised 3.7kb (-α3.7) and 4.2kb (-α4.2) deletions which were found in 172 (66.15%) and 5 (1.92%) alleles, respectively. The incidence of non-deletional α+-thal in decreasing order was Hb Constant Spring (Hb CS, αCS) 28.85%, Hb Quong Sze (Hb QS, αQS) 1.54%, and Hb Paksé (Hb PS, αPS) 0.77%. The genotype characterization of Hb H disease and the development of the RDB technic for detection of α-thal mutations presented in this study enable the prenatal diagnosis of Hb Bart's hydrops fetalis syndrome.

Invasive prenatal diagnosis of α-thalassemia to control Hb Bart's hydrops fetalis syndrome: 15years of experience.

The aim of the present study was to report experiences with invasive prenatal diagnosis of α-thalassemia for the prevention of Hb Bart's hydrops fetalis syndrome in the Guangxi Zhuang Autonomous Region, China. Pregnant women and their partners who tested positive for α0-thalassemia or were diagnosed with HbH diseases were counseled and suggested to undergo a prenatal diagnostic procedure for α-thalassemia. Fetal material was obtained by chorionic villus sampling (CVS) between 9 and 13weeks of gestation, by amniocentesis between 16 and 24weeks of gestation and by cordocentesis after 24weeks of gestation. The α0-thalassemia gene types were detected by gap polymerase chain reaction (Gap-PCR). All results were finally confirmed by DNA analysis after delivery or termination of pregnancy. An invasive prenatal α-thalassemia diagnosis was performed in 3155 cases at risk for Hb Bart's hydrops fetalis syndrome at our hospital from 2002 to 2016. CVS was performed in 1559 cases (49.4%), amniocentesis in 1240 cases (39.3%) and cordocentesis in 356 cases (11.3%). In total, 786 fetuses were diagnosed as Hb Bart's hydrops fetalis syndrome. Among these cases, the α-thalassemia genotype was --SEA/--SEA in 784 cases and --SEA/--THAI in 2 cases. All affected pregnancies were terminated in time. This extensive experience suggests that carrier screening, molecular diagnostics, genetic counselling, and prenatal diagnosis are effective measures to prevent Hb Bart's hydrops fetalis syndrome.

Outcomes and morbidities of patients who survive haemoglobin Bart's hydrops fetalis syndrome: 20-year retrospective review.

Haemoglobin Bart's hydrops fetalis syndrome was once considered a fatal condition. However, advances over the past two decades have enabled survival of affected patients. Data relating to their morbidities and outcomes will help medical specialists formulate a management plan and parental counselling. All babies with the syndrome who survived beyond the neonatal period and were subsequently managed long-term in eight public hospitals in Hong Kong from 1 January 1996 to 31 December 2015 were included. Patient and parent characteristics, antenatal care, reasons for continuation of pregnancy, intrauterine interventions, perinatal course, presence of congenital malformations, stem-cell transplantation details, and long-term neurodevelopmental outcomes were reviewed. A total of nine patients were identified, of whom five were female and four male. The median follow-up duration was 7 years. All were Chinese and were homozygous for the Southeast Asian α-thalassaemia deletion. Five of the nine mothers received antenatal care at a public hospital and opted to continue the pregnancy after antenatal diagnosis and counselling. Despite intrauterine transfusions, all babies were born with respiratory depression and required intubation and mechanical ventilation during the neonatal period. Hypospadias was identified in all four male infants. Growth retardation, global developmental delay, and residual neurological deficits were noted in two-thirds of the patients. Haematopoietic stem-cell transplantation was performed in two patients, who became transfusion-independent. Survival of patients with Bart's hydrops fetalis syndrome is possible but not without short- and long-term complications; local epidemiology is comparable to that documented for an international registry. Detailed antenatal counselling of parents with a non-judgemental attitude and cautious optimism are imperative.

Molecular prenatal diagnosis of alpha and beta thalassemia in pregnant Hakka women in southern China.

To date, there has been no systematic study of DNA-based prenatal diagnosis of thalassemia in pregnant Hakka women in southern China. A total of 279 pregnant Hakka women with confirmed cases of thalassemia who had been treated at the Meizhou People's Hospital in China's Guangdong Province from January 2014 to December 2016 were here enrolled. Genomic DNA was extracted from peripheral blood of couples and villus, amniotic fluid, or fetal cord blood. DNA-based diagnosis was performed on the tissues of fetuses whose parents had tested positive for α- and β-globin gene mutations were found using polymerase chain reaction (PCR) and flow-through hybridization technique. Follow-up visits were performed 6months after the fetuses were born. Prenatal diagnosis was performed on 279 fetuses in at-risk pregnancies. Here, 211 α-thalassemia fetuses were confirmed, including 41 (19.43%) that tested positive for Bart's hydrops syndrome and 15 (7.11%) for Hb H disease. There were 103 (48.81%) heterozygotes. β-thalassemia was confirmed in 68 fetuses, including 23 (33.82%) with severe thalassemia and 27 (39.71%) heterozygotes. Another 12 cases were confirmed with α+β-thalassemia, including three cases of severe β-thalassemia. DNA-based testing prenatal diagnosis of thalassemia was found to be highly reliable. Our findings provide key information for clinical genetic counseling of prenatal diagnosis for major thalassemia in pregnant Hakka women in southern China.

Detection of SEA-type α-thalassemia in embryo biopsies by digital PCR

ObjectiveAccurate and efficient pre-implantation genetic diagnosis (PGD) based on the analysis of single or oligo-cells is needed for timely identification of embryos that are affected by deleterious genetic traits in in vitro fertilization (IVF) clinics. Polymerase chain reaction (PCR) is the backbone of modern genetic diagnoses, and a spectrum of PCR-based techniques have been used to detect various thalassemia mutations in prenatal diagnosis (PND) and PGD. Among thalassemias, SEA-type α-thalassemia is the most common variety found in Asia, and can lead to Bart's hydrops fetalis and serious maternal complications. Materials and methodsTo formulate an efficient digital PCR for clinical diagnosis of SEA-type α-thalassemia in cultured embryos, we conducted a pilot study to detect the α-globin and SEA-type deletion alleles in blastomere biopsies with a highly sensitive microfluidics-based digital PCR method. Genomic DNA from embryo biopsy samples were extracted, and crude DNA extracts were first amplified by a conventional PCR procedure followed by a nested PCR reaction with primers and probes that are designed for digital PCR amplification. ResultsAnalysis of microfluidics-based PCR reactions showed that robust signals for normal α-globin and SEA-type deletion alleles, together with an internal control gene, can be routinely generated using crude embryo biopsies after a 106-fold dilution of primary PCR products. ConclusionThe SEA-type deletion in cultured embryos can be sensitively diagnosed with the digital PCR procedure in clinics. The adoption of this robust PGD method could prevent the implantation of IVF embryos that are destined to develop Bart's hydrops fetalis in a timely manner. The results also help inform future development of a standard digital PCR procedure for cost-effective PGD of α-thalassemia in a standard IVF clinic.

Co-inheritance of α0 -thalassemia elevates Hb A2 level in homozygous Hb E: Diagnostic implications.

Differentiation of homozygous hemoglobin (Hb) E with and without α0 -thalassemia is subtle on routine hematological ground. We examined in a large cohort of homozygous Hb E if the level of Hb A2 is helpful. A total of 592 subjects with homozygous Hb E were recruited from ongoing thalassemia screening program. Additionally, five couples at risk of having fetuses with Hb Bart's hydrops fetalis who were homozygous Hb E were also investigated. Hb analysis was performed using capillary electrophoresis system. Globin genotypes were defined by DNA analysis. Subjects were classified into four groups including pure homozygous Hb E (n=532), homozygous Hb E/α0 -thalassemia (n=48), Hb Constant Spring EE Bart's disease (n=8), and Hb EE Bart's disease (n=4). The levels of Hb A2 were found, respectively, to be 4.97±0.69, 6.64±1.02, 4.86±0.87, and 7.60±1.04%. Among five couples at risk, α0 -thalassemia was identified in three subjects with Hb A2 >6.0%. Increased Hb A2 level is a useful marker for differentiation of homozygous Hb E with and without α0 -thalassemia. This should lead to a significant reduction in number of referral cases of homozygous Hb E for molecular testing of α0 -thalassemia in routine practice.

Alpha thalassemia deletions found in suspected cases of beta thalassemia major in Pakistani population.

Background & Objective:Alpha (α) thalassemia is a hereditary disorder and is caused by deletions or mutations in globin genes. It is present in two clinically significant forms: hemoglobin Bart hydrops fetalis (Hb Bart) syndrome and hemoglobin H (HbH) disease. It is highly prevalent in South-East Asia or Mediterranean countries. The most common deletion reported in alpha thalassemia in Pakistani population was –α3.7 with a frequency of 8.3%, and the rare forms were –α4.2 (0.2%) and αααanti3.7 (0.9%). In our study, diagnosis of severe anemia cases without any α and β mutations or deletions were made by using extended alpha thalassemia deletions panel. The main objective of this study was to determine the prevalence and to study the spectra of alpha thalassemia gene deletions in beta thalassemia patients with the use of an extended panel including −−SEA, −−FIL, −−MED, −−20.5, −−THAI in addition to –α3.7, –α4.2 & -αααanti3.7.Methods:The samples were collected in ethylenediaminetetraacetic acid (EDTA) vacutainers. A total of 156 samples were analyzed for alpha thalassemia mutations. This cohort included 121 samples of beta thalassemia major, nine samples of beta thalassemia minor and 26 without any evidence of beta thalassemia mutations. DNA was extracted with Qiagen extraction kit. The primers for determination of different subsets of alpha thalassemia deletions were included. PCR amplification was performed and result interpreted on agarose gel.Results:Co-inheritance of alpha thalassemia (–α3.7, –α4.2) with homozygous beta thalassemia was detected in 30% cases of studied cohort (37 out of 121). The most common found was –α3.7 deletion (35/37) as single/double deletions or in combination with -αααanti3.7. In undiagnosed cases screened for beta thalassemia major, we found Mediterranean (–αMED) deletion at specifically 875 bp on agarose gel. This is distinctive finding in case of detecting –αMED instead of any other deletion from Pakistan.Conclusion:Alpha thalassemia deletions (–α3.7, –α4.2) are the common co-inherited deletions found in beta thalassemia major patients. On the basis of results, we propose an extended alpha thalassemia genetic mutation panel should be used for screening of children presenting with anemia with suspicion of haemoglobinopathy.

Occurrence of the – –SEA, – –THAI and – –FIL α-Thalassemia-1 Carriers from a 7-Year Study at Ramathibodi Hospital, Bangkok, Thailand

α-Thalassemia (α-thal) is one of the most common genetic diseases in Thailand. Homozygosity of α-thal-1 (– –/– –) and compound heterozygosity of α-thal-1/α-thal-2 (– –/–α) leads to Hb Bart's (γ4) hydrops fetalis and Hb H (β4) disease, respectively. In order to better control and provide prevention of α-thal disease, the prevalence of α-thal-1 carriers and the types of genotypes in the Thai population should be known. A 7-year retrospective study, employing multiplex gap-polymerase chain reaction (gap-PCR) of 31,632 blood samples from Ramathibodi Hospital, Mahidol University, Bangkok, revealed an α-thal-1 carrier rate of 14.40% with the – –SEA (NG_000006.1: g.26264_45564del19301), – –THAI (NG_000006.1: g.10664_44164del33501) and – –FIL (NG_000006.1: g.11684_43534del31851) genotypes, constituting frequencies of 14.21, 0.18 and 0.01%, respectively. Although the – –FIL genotype is rare in the Thailand, its detection should be included in future α-thal screening programs.

Prenatal diagnosis of Thailand deletion of α-thalassemia 1 families

To conduct analysis and prenatal diagnosis on 11 couples carrying Thailand deletion (--(THΑI)) α-thalassemia 1, so as to provide information for clinical genetic counseling on α-thalassemia 1. Altogether 11 Thailand deletion (--(THΑI)) α-thalassemia 1 families were collected from Fujian Maternal and Children Health Hospital from May 2009 to September 2015. Gap-polymerase chain reaction (gap-PCR) and reverse dot blot (RDB) technology were used to detect the thalassemia mutations in the couples and fetuses. In one family, Thailand deletion α-thalassemia 1 was detected in both the pregnant woman and her husband. In 10 families, Thailand deletion α-thalassemia 1 was detected in either the pregnant women or the husband, while the spouses had α-thalassemia heterozygote (1 combined with β thalassemia heterozygote). Thailand deletion α-thalassemia 1 family members all had lower mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH). In prenatal diagnosis of the 12 fetuses, 4 fetuses were found with hemoglobin(Hb) Bart's hydrops fetalis syndrome, 5 were with α-thalassemia heterozygote, and 3 were normal. For couples with positive hematological phenotype but normal results in routine genetic examination of α-thalassemia, attention should be paid especially for with a history of having babies of hydrops fetalis syndrome or hemoglobin H disease. It is necessary to consider the possibility of the rare Thailand deletion (--(THΑI)) α-thalassemia 1. Prenatal diagnosis for high-risk families plays an important role.