Molecular characterization of a novel 83.9-kb deletion of the α-globin upstream regulatory elements by long-read sequencing

Inherited deletions of upstream regulatory elements of α-globin genes give rise to α-thalassemia, which is an autosomal recessive monogenic disease. However, conventional thalassemia target diagnosis often fails to identify these rare deletions. Here we reported a family with two previous pregnancies of Hb Bart's hydrops fetalis and was seeking for prenatal diagnosis during the third pregnancy. Both parents had low level of Hemoglobin A2 indicating α-thalassemia. Conventional Gap-PCR and PCR-reverse dot blot showed the father carried -SEA deletion but did not identify any variants in the mother. Multiplex ligation-dependent probe amplification identified a deletion containing two HS-40 probes but could not determine the exact region. Finally, a long-read sequencing (LRS)-based approach directly identified that the exact deletion region was chr16: 48,642-132,584, which was located in the α-globin upstream regulatory elements and named (αα)JM after the Jiangmen city. Gap-PCR and Sanger sequencing confirmed the breakpoint. Both the mother and fetus from the third pregnancy carried heterozygous (αα)JM, and the fetus was normally delivered at gestational age of 39 weeks. This study demonstrated that LRS technology had great advantages over conventional target diagnosis methods for identifying rare thalassemia variants and assisted better carrier screening and prenatal diagnosis of thalassemia.

Ten years' experience in prenatal diagnosis of α-thalassemia in a municipal hospital and retrospective analysis of ultrasonic abnormalities

OBJECTIVE

This study reviewed and analyzed the prenatal diagnosis experience of thalassemia in our center over the past decade and the abnormal ultrasonic characteristics of fetuses with hemoglobin (Hb) Bart's hydrops fetalis.

METHODS

Pregnant women and their partners who tested positive for α0-thalassemia or were diagnosed with thalassemia intermedia (HbH diseases) underwent genetic counseling, and a prenatal diagnostic procedure for α-thalassemia was recommended. Ultrasonography was performed before prenatal diagnosis.

RESULTS

Invasive prenatal α-thalassemia diagnosis and ultrasonography were performed in 1049 patients at risk for Hb Bart's hydrops fetalis syndrome at our hospital from 2012 to 2021. Chorionic villus sampling (CVS) was performed in 58 cases (5.5%), amniocentesis in 902 cases (86%), and cordocentesis in 89 cases (8.5%). Hb Bart's hydrops fetalis syndrome was diagnosed in 280 fetuses. The most common body cavity effusion was pericardial effusion, ascites, and fetal systemic edema.

CONCLUSIONS

The extensive experience at our center shows that carrier screening, molecular diagnostics, genetic counseling, and prenatal diagnosis are effective measures to prevent Hb Bart's hydrops fetalis syndrome. The ultrasonographic abnormalities in fetuses with Hb Bart's hydrops are mainly caused by an increase in cardiac output, which leads to the body cavity effusion from various organs.

Identification of a novel 10.3 kb deletion causing α0-thalassemia by third-generation sequencing: Pedigree analysis and genetic diagnosis

BACKGROUND

α-thalassemia is an inherited blood disorder caused by variants in the α-globin gene cluster. Identification of the pathogenic α-globin gene variants is important for the diagnosis and management of thalassemia.

METHODS

Two suspected families from Xiantao, Hubei Province were recruited in this study. The family members underwent hemoglobin testing. Polymerase Chain Reaction based reverse dot blot (PCR-RDB) was employed to identify the known variants. Next-generation sequencing (NGS) and third-generation sequencing (TGS) were performed to screen the potential disease-causing variants, which were validated by Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA).

RESULTS

Hematological analysis suggested that proband A had α-thalassemia traits, and proband B had HbH disease traits. However, only a -α^3.7 mutation had been detected by PCR-RDB and NGS in the proband of family B. Subsequent TGS identified a novel 10.3 kb deletion (NC_000016.10:g.172342-182690del) covering the HBA1, HBQ1 and HBA2 genes in the α-globin gene cluster in both family A and B, which was confirmed by Sanger sequencing and MLPA. These results indicated that the novel deletion is likely responsible for α-thalassemia.

CONCLUSION

A novel α-thalassemia deletion was identified for the two families by TGS. Our work broadened the molecular spectrum of α-thalassemia, and was beneficial for the diagnosis, genetic counseling and management of α-thalassemia.

Using affected embryos to establish linkage phase in preimplantation genetic testing for thalassemia

BACKGROUND

This study aimed to evaluate the ability of next-generation sequencing (NGS) to conduct preimplantation genetic testing (PGT) for thalassemia using affected embryos.

METHODS

This study included data from 36 couples who underwent PGT for thalassemia without probands and relative pedigrees. NGS results were compared with prenatal diagnosis results.

RESULTS

Thirty-six couples (29 α-thalassemia and 7 β-thalassemia) underwent 41 PGT cycles (31 α-thalassemia and 10 β-thalassemia). Analysis using NGS produced conclusive results for all biopsied blastocysts (100%, 217/217). One hundred and sixty (73.7%, 160/217) were unaffected by thalassemia. Preimplantation genetic testing for aneuploidy revealed that 112 (70.0%, 112/160) were euploid. Single blastocysts were transferred into the uteri of 34 women (53 frozen embryo transfer [FET] cycles). Thirty-two cycles resulted in clinical pregnancies, with a clinical pregnancy rate of 60.1% (32/53) per FET cycle. Twenty-two cycles (22 couples) resulted in 23 live births, with a live birth rate of 43.4% (23/53; 3 cycles were ongoing pregnancies). All 25 embryos' prenatal diagnosis results and/or thalassemia gene analyses after delivery were concordant with the NGS-PGT results. Seven embryos (21.9%, 7/32) were miscarried before 12 weeks' gestation, and the abortion villus in four showed a normal karyotype and thalassemia results consistent with the NGS-PGT results. Aborted fetus samples from 3 cycles were not available because the pregnancy lasted less than 5 weeks.

CONCLUSION

NGS can be used to conduct PGT for thalassemia using affected embryos as a reference.

TRIAL REGISTRATION

Retrospectively registered.

Discordantly high HbA1c may assist in diagnosing α-thalassemia but not diabetes: A case report

Glycated hemoglobin (HbA1c) is an important method for monitoring blood glucose and diagnosing diabetes. High‐performance liquid chromatography is more commonly used in the laboratory for the detection of HbA1c. Although HbA1c detected by high‐performance liquid chromatography is susceptible to abnormal hemoglobin, there are few reports that it is affected by α‐thalassemia. Previous reports have generally concluded that α‐thalassemia does not affect or lower HbA1c. Here, we report a case of discordantly high HbA1c inconsistent with fasting blood glucose. Finally, the patient was diagnosed with α‐thalassemia and insulin resistance. α‐Thalassemia might lead to a discordantly high HbA1c result, which could be attributed to elevated hemoglobin H. In this case, glycated albumin might accurately reflect the real average level of blood glucose. When finding discordant HbA1c, patients should be advised to undergo thalassemia and hemoglobinopathy screening by diabetologists/endocrinologists or primary care physicians to avoid a missed diagnosis of hematopathy.

Alpha thalassemia, but not βS-globin haplotypes, influence sickle cell anemia clinical outcome in a large, single-center Brazilian cohort

Alpha thalassemia and beta-globin haplotype are considered classical genetic disease modifiers in sickle cell anemia (SCA) causing clinical heterogeneity. Nevertheless, their functional impact on SCA disease emergence and progression remains elusive. To better understand the role of alpha thalassemia and beta-globin haplotype in SCA, we performed a retrospective study evaluating the clinical manifestations of 614 patients. The univariate analysis showed that the presence of alpha-thalassemia -3.7-kb mutation (αα/-α and -α/-α) decreased the risk of stroke development (p = 0.046), priapism (p = 0.033), and cholelithiasis (p = 0.021). Furthermore, the cumulative incidence of stroke (p = 0.023) and cholelithiasis (p = 0.006) was also significantly lower for patients carrying the alpha thalassemia -3.7-kb mutation. No clinical effects were associated with the beta-globin haplotype analysis, which could be explained by the relatively homogeneous haplotype composition in our cohort. Our results reinforce that alpha thalassemia can provide protective functions against hemolysis-related symptoms in SCA. Although, several genetic modifiers can impact the inflammatory state of SCA patients, the alpha thalassemia mutation remains one of the most recurrent genetic aberration and should therefore always be considered first.

Noninvasive prenatal testing of α-thalassemia and β-thalassemia through population-based parental haplotyping

Background

Noninvasive prenatal testing (NIPT) of recessive monogenic diseases depends heavily on knowing the correct parental haplotypes. However, the currently used family-based haplotyping method requires pedigrees, and molecular haplotyping is highly challenging due to its high cost, long turnaround time, and complexity. Here, we proposed a new two-step approach, population-based haplotyping-NIPT (PBH-NIPT), using α-thalassemia and β-thalassemia as prototypes.

Methods

First, we deduced parental haplotypes with Beagle 4.0 with training on a large retrospective carrier screening dataset (4356 thalassemia carrier screening-positive cases). Second, we inferred fetal haplotypes using a parental haplotype-assisted hidden Markov model (HMM) and the Viterbi algorithm.

Results

With this approach, we enrolled 59 couples at risk of having a fetus with thalassemia and successfully inferred 94.1% (111/118) of fetal alleles. We confirmed these alleles by invasive prenatal diagnosis, with 99.1% (110/111) accuracy (95% CI, 95.1–100%).

Conclusions

These results demonstrate that PBH-NIPT is a sensitive, fast, and inexpensive strategy for NIPT of thalassemia.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13073-021-00836-8.

Molecular spectrum of α-thalassemia mutations in Erbil province of Iraqi Kurdistan

α-Thalassemia is a globally prevalent genetic disorder of hemoglobin (Hb) structure where the rate of α-globin chain synthesis is reduced or absent based on the underlying α-globin mutation(s). This study aimed to define the spectrum of α-globin gene mutations and assess their relative frequency within a group of α-thalassemia carriers. A total of 96 young subjects with unexplained hypochromia and microcytosis were recruited. They were referred from the premarital hemoglobinopathy screening and genetic counseling center in Erbil. All subjects were genetically tested for 21 common α-globin gene mutations using multiplex PCR and reverse hybridization. Six different α-globin gene mutations and nine different genotypes were detected in 84 carrier subjects. Their mean Hb was 12.9 (± 1.29) g/dL, of whom 49 subjects (58.3%) had a normal Hb level. The two most frequently encountered mutations were -α^3.7 deletion (62.86%) and α2^-5nt mutation (20%). Deletions were encountered in 71.43% of the mutated alleles. The most commonly observed genotype was -α^3.7/αα (46.43%), followed by -α^3.7/-α^3.7 and α^-5ntα/αα genotypes (10.72% each). Carriers of α^poly-A1α/αα and -α^3.7/-α^-5ntα genotypes showed significantly lower Hb, mean cell volume, and mean cell Hb values comparing to carriers of most other genotypes. In our population, the spectrum of α-globin mutations was confined to a limited number of mutations with deletions being mostly observed.

Eleven healthy live births: a result of simultaneous preimplantation genetic testing of α- and β-double thalassemia and aneuploidy screening

PURPOSE

To evaluate the efficacy of preimplantation genetic testing (PGT) for α- and β-double thalassemia combined with aneuploidy screening using next-generation sequencing (NGS).

METHODS

An NGS-based PGT protocol was performed between 2017 and 2018 for twelve couples, each of which carried both α- and β-thalassemia mutations. Trophectoderm biopsy samples underwent whole-genome amplification using multiple displacement amplification (MDA), followed by NGS for thalassemia detection and aneuploidy screening. A selection of several informative single nucleotide polymorphisms (SNPs) established haplotypes. Aneuploidy screening was performed only on unaffected noncarriers and carriers. Unaffected and euploid embryos were transferred into the uterus through frozen-thawed embryo transfer (FET).

RESULTS

A total of 280 oocytes were retrieved following 18 ovum pick-up (OPU) cycles, with 182 normally fertilized and 112 cultured to become blastocysts. One hundred and seven (95.5%, 107/112) blastocysts received conclusive PGT results, showing 56 (52.3%, 56/107) were unaffected. Thirty-seven (66.1%, 37/56) of the unaffected were also identified as euploid. One family had no transferable embryos. Unaffected and euploid embryos were then transferred into the uterus of the other 11 couples resulting in 11 healthy live births. The clinical pregnancy rate was 61.1% (11/18) per OPU and 68.8% (11/16) per FET, with no miscarriage reported. Seven families accepted the prenatal diagnosis and received consistent results with the NGS-based PGT.

CONCLUSION

This study indicated that NGS could realize the simultaneous PGT of double thalassemia and aneuploidy screening in a reliable and accurate manner. Moreover, it eliminated the need for multiple biopsies, alleviating the potential damages to the pre-implanted blastocysts.

Alpha-Thalassemia Carrier due to -α3.7 Deletion: Not So Silent

BACKGROUND/OBJECTIVE

Alpha-thalassemia is one of the most prevalent genetic diseases, with the -α3.7 deletion being the most common mutation. Molecular studies have suggested mechanisms to explain the mild phenotype of "silent carrier" heterozygotes. However, the correlation between the clinical laboratory picture and the -α3.7 heterozygous state remains unclear, thus we chose to investigate.

METHODS

We analyzed the medical files of 192 children evaluated for microcytosis at our tertiary center between 2007 and 2017 and diagnosed as heterozygotes for the -α3.7 deletion. Additional α-thalassemia mutations, iron deficiency anemia, and β-thalassemia were ruled out. Laboratory parameters were compared to age- and sex-matched reference values.

RESULTS

The -α3.7 carriers had significantly lower Hb and mean corpuscular volume (MCV) than the reference population, and significantly higher red blood cell counts across all age groups. The greatest reduction in Hb level appeared among male adolescents, while MCV was consistently 2 SDs lower than normal in most patients older than 2 years.

CONCLUSION

Heterozygosity for the -α3.7 deletion was associated with clinically significant microcytosis and mild anemia in our pediatric population. In the absence of iron deficiency and β-thalassemia, this finding provides a diagnosis for mild microcytic anemia, making additional investigations of microcytosis unnecessary.

Molecular analysis of a large novel deletion causing α+-thalassemia

BACKGROUND

α-thalassaemia is an inherited blood disorder caused by mutations in the α-globin gene cluster. Recognizing the pathogenic α-globin gene mutations associated with α-Thalassemia is of significant importance to thalassaemia's diagnosis and management.

METHODS

A family with α-thalassaemia from Fujian, China was recruited for this study. The phenotype was confirmed through haematological analysis. Commercially available Gap-PCR genotypic methods were employed to identify the known deletions causing α-thalassemia. MLPA analysis was used to study the novel mutations; this was then confirmed through DNA sequencing and bioinformatics analysis.

RESULTS

The proband of the family belonged to Southeast Asian type (--^SEA) thalassaemia. None of the known mutations associated with α-thalassaemia were detected in this family's genetics, whereas a novel 6.9 kb deletion (16p13.3 g.29,785-36,746) covering the α2 gene on the globin gene cluster was identified with MLPA and confirmed through Sanger Sequencing. This data led us to propose a novel pathogenic deletion associated with α-thalassemia: -α^6.9 /--^SEA.

CONCLUSIONS

A novel α-thalassaemia deletion was identified in members of a Chinese family and subsequently analyzed. This finding has helped broaden the spectrum of pathogenic mutations leading to the development of α-thalassaemia, paving the way for improved disease diagnosis and management.

Increased endothelial activation in α-thalassemia disease

One complication of thalassemia is thromboembolism (TE), which is caused by an abnormal red blood cell surface, as well as endothelial and platelet activation. These findings are commonly observed in severe β-thalassemia. However, limited information on α-thalassemia exists. This study enrolled subjects with deletional and non-deletional α-thalassemia and normal controls (NC). Plasma and serum of subjects were tested for endothelial activation markers including thrombomodulin (TM), vascular cell adhesion molecule-1 (VCAM-1), and von Willebrand factor antigen as well as platelet activation markers including thromboxane B2 and platelet factor 4. A total of 179 subjects were enrolled: 29 in the deletional group (mean age 13.3 ± 4.4 years), 31 in the non-deletional group (mean age 12.9 ± 4.8 years), and 119 in the NC group (mean age 13.6 ± 3.0 years). Twenty nine percent of subjects in the non-deletional group received regular red blood cell transfusion and iron chelator administration. Serum ferritin level was higher in the non-deletional group than that in the deletional group. Multivariate analysis demonstrated that VCAM-1 and TM levels were increased significantly in α-thalassemia compared with NC group (816.8 ± 131.0 vs 593.9 ± 49.0 ng/ml, and 4.9 ± 0.7 vs 4.0 ± 0.4 ng/ml, P < 0.001 respectively). VCAM-1 and TM levels in the non-deletional group were significantly higher than that in the deletional group. The present study demonstrated endothelial activation in children with α-thalassemia disease, especially those in the non-deletional group, which might be one risk factor for TE in α-thalassemia disease.

[Rapid preimplantation genetic diagnosis of α-thalassemia SEA deletion with blastocyst cell whole genome amplification and short fragment Gap-PCR method]

OBJECTIVE

To develop a rapid preimplantation genetic diagnosis method for α-thalassemia SEA deletion based on blastocyst cell whole genome amplification (WGA) combined with short fragment Gap-PCR.

METHODS

Using multiple displacement amplification (MDA) WGA technique, we established a double-fluorescent PCR system of the housekeeping genes GAPDH and β-actin for WGA quality testing, and a genotyping PCR system of mutant and normal short sequences for α-thalassemia SEA deletion. The sensitivity and accuracy of this method for diagnosis of α-thalassemia SEA deletion were evaluated by detecting lymphocyte samples containing different cell numbers from carriers of SEA deletion. The applicability of this method was evaluated by testing of 12 blastocyst biopsy samples.

RESULTS

Detection of lymphocyte samples with different cell numbers using the method developed in this study revealed no ADO in 3-cell samples, and the product quantity of WGA became stable for 4-cell samples. Genotyping of the 10 blastocyst biopsy samples with successful WGA showed a genotype of --^SEA/αα in 5 samples and αα/αα in the other 5 samples, which were consistent with the verification results.

CONCLUSIONS

The method developed in this study is a complete testing process for 4-6 blastocyst biopsy cells to allow rapid, accurate, and cost-effective PGD genotyping of α-thalassemia SEA deletion using short fragment gap-PCR.

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

PURPOSE

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.

METHODS

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 13 weeks of gestation, by amniocentesis between 16 and 24 weeks of gestation and by cordocentesis after 24 weeks 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.

RESULTS

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.

CONCLUSIONS

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.

Molecular Basis of α-Thalassemia in Iran

Alpha-thalassemia (α-thal) is probably the most prevalent monogenic condition in the world. Deletions are the most common types of mutations in α-thal, followed by point mutations and small insertion/deletion. In the context of national screening program for prevention of thalassemia and hemoglobinopathies in Iran, α-thal carriers have come to more attention. Therefore, the frequency and distribution of α-globin mutations in various regions of the country have been studied in recent years. A comprehensive search was performed in PubMed, Scopus, and national databases for finding reports on mutation detection in α-thal carriers and HbH disease with Iranian origin. The mutation data of 10849 α-thal carriers showed that -α^3.7 and α^-5NT were the most common deletional and nondeletional mutations, respectively. In HbH disease cases, the -α^3.7/--^MED was the most prevalent genotype. Overall, 42 different mutations have been identified in α-globin cluster reflecting the high heterogeneity of the mutations in Iranian populations.

Introduction of novel α1-hemoglobin gene mutation with transfusion-dependent phenotype

OBJECTIVE AND IMPORTANCE

Thalassemia is the most frequently monogenetic disorders around the world that is inherited as a recessive single-gene disease, resulting from mutations in α- or β-globin gene clusters. The aim of this report was to present a new insertional mutation in the α₁ globin gene which causes transfusion-dependent anemia in α-thalassemic patients.

CLINICAL PRESENTATION

Two 5-year-old girls with blood transfusion-dependent α-thalassemia anemia and another girl with moderate α-thalassemia have been presented among patients who have been referred to Hematology and Thalassemia Research Center, Dastgheib Hospital, Shiraz, Iran. They were not relatives. All children were stunted and pale; they were put on regular blood transfusion every 14-21 days.

INTERVENTION

Sequencing of the β-globin gene was normal in all cases and their parents; but, α-globin gene sequencing results were remarkable. An insertion of 21 base pairs (IVS II+3ins (+21nt)(+GACCCGGTCAACTTCAAGGTG) in the α₁-globin gene was detected in all three cases and one of their parents. In two cases, this insertion was accompanied by MED deletion and in one child by POLY A₁ mutation. MED deletion was detected by gap-PCR.

CONCLUSION

This new 21 base pair insertion cannot affect blood parameters on its own, but can present as continuous blood transfusion-dependent α-thalassemia. Thus, it is important to take this point into account for detecting the carriers, like β-thalassemia carriers, which can present as transfusion-dependent children in parents with α-thalassemia trait.

Detection of α-Thalassemia by Using Multiplex Ligation-Dependent Probe Amplification as an Additional Method for Rare Mutations in Southern Turkey

α-thalassemia is the most common single gene disorder in the Cukurova Region in Turkey. It is therefore routinely screened, including premaritally, in our region. The heterogeneous molecular basis of the disease makes α-thalassemia mutation detection difficult and complex. Besides well established methods, multiplex ligation dependent probe amplification (MLPA) is known as an effective, simple and specific method for the detection and characterization of deletions and duplications. We employed MLPA testing to 30 patients with hematological parameters suggestive of α-thalassemia carrier status but was negative for α-thalassemia with conventional reverse dot blot hybridization (RDB). We found α-globin gene deletions in 3 out of 30 (10 %) patients with MLPA. We propose that MLPA can be used as a second tier test in addition to other techniques such as RDB to identify α-thalassemia carriers in high prevalence regions such as ours, thereby allowing clinicians to provide accurate genetic counselling.

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 α(0)-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.

Characterization of Hb Calvino (HBB: c.406G > A): a new silent β-globin gene variant found in coexistence with α-thalassemia in a family of African origin

We report a new silent β-globin gene variant found in a family from Angola living in the north eastern Italian city of Ferrara. The probands, two young sisters, presented with hematological parameters compatible with a β-thalassemia (β-thal) minor but with normal Hb A₂ levels and normal hemoglobin (Hb) separation on high performance liquid chromatography (HPLC). Molecular analyses revealed a homozygosity for the common -α(3.7) (rightward) deletion and heterozygosity for a novel transition (GCT > ACT) at codon 135 of the β-globin gene, leading to an Ala → Thr single amino acid substitution that was inherited from the healthy father.

Hemoglobin α in the blood vessel wall

Hemoglobin has been studied and well characterized in red blood cells for over 100 years. However, new work has indicated that the hemoglobin α subunit (Hbα) is also found within the blood vessel wall, where it appears to localize at the myoendothelial junction (MEJ) and plays a role in regulating nitric oxide (NO) signaling between endothelium and smooth muscle. This discovery has created a new paradigm for the control of endothelial nitric oxide synthase activity, nitric oxide diffusion, and, ultimately, vascular tone and blood pressure. This review discusses the current knowledge of hemoglobin׳s properties as a gas exchange molecule in the bloodstream and extrapolates the properties of Hbα biology to the MEJ signaling domain. Specifically, we propose that Hbα is present at the MEJ to regulate NO release and diffusion in a restricted physical space, which would have powerful implications for the regulation of blood flow in peripheral resistance arteries.

Implementation of newborn screening for hemoglobin h disease in mainland china

Hemoglobin H disease is the most severe non-fatal form of α-thalassemia syndrome characterized by pronounced microcytic hypochromic hemolytic anemia. It is predominantly seen in Southeast Asia, the Middle East and the Mediterranean. Studies suggest that hemoglobin H disease is not as benign a disorder as previously thought. Newborn screening for hemoglobin H disease is especially appealing because the screening test is based on the detection of hemoglobin Bart's (γ4) that is only possible within the newborn period. In this study, we reported on a 4-year period of newborn screening program at a mainland Chinese hospital, which detected 35 babies with hemoglobin H disease in a total of 26 152 newborns. The overall prevalence for hemoglobin H disease among all newborns in southern China is ~1 in 1,000. These children need appropriate follow-up and potential comprehensive care during their growth and development.

Prenatal control of Hb Bart's hydrops fetalis: a two-year experience at a mainland Chinese hospital

α-Thalassemia is a common inherited disease in southern China. The severest form is Hb Bart's hydrops fetalis, in which the affected fetuses almost always die in utero or shortly after birth, and the mothers are at high risk for severe morbidity. Therefore, this condition should be controlled, especially prenatally. In this study, we reported on a two-year experience in prenatal control of Hb Bart's hydrops fetalis at a mainland Chinese hospital. Totally, 573 pregnancies at risk for Hb Bart's hydrops fetalis were referred and different prenatal procedures were offered depending on the gestational age at presentation. One hundred fifty-two affected fetuses were diagnosed prenatally; among these, only half presented in early gestation, and were terminated in time. Although our prenatal program has successfully prevented the birth of children with severe thalassemia, it does not show a satisfactory outcome, considering the gestational age when an affected pregnancy is terminated.

A Case of Nonimmune Hydrops Fetalis Caused by Homozygous α-Thalassemia

Hydrops fetalis is a serious condition which indicates poor prognosis for the affected fetus. Although the incidence of isoimmune hydrops fetalis has decreased markedly, nonimmune hydrops fetalis cases have been more frequently reported. Nonimmune-mediated hydrops can be caused by hemoglobinopathies. In this report we present a case of nonimmune hydrops fetalis caused by homozygous α-thalassemia. Because of the high incidence of the disease in our country, α-thalassemia should be investigated in all cases with nonimmune hydrops fetalis.

Conflict of interest:None declared.

Clinical characteristics of pediatric thalassemia in Korea: a single institute experience

Few literatures have elaborated on the clinical characteristics of children with thalassemia from low-prevalence areas. A retrospective analysis was conducted on children genetically confirmed with thalassemia at Seoul National University Children's Hospital in Korea. Nine children (1α thalassemia trait, 6β thalassemia minor, 2β thalassemia intermedia) were diagnosed with thalassemia at median age of 4.3 yr old with median hemoglobin of 9.7 g/dL. Seven (78%) children were incidentally found to be anemic and only 2 with β thalassemia intermedia had presenting symptoms. Five children (56%) were initially misdiagnosed with iron deficiency anemia. Despite the comorbidities due to α thalassemia mental retardation syndrome, the child with α thalassemia trait had mild hematologic profile. Children with β thalassemia intermedia had the worst phenotypes due to dominantly inherited mutations. None of the children was transfusion dependent and most of them had no complications associated with thalassemia. Only 1 child (11%) with codon 60 (T→A) mutation of the HBB gene needed red blood cell transfusions. He also had splenomegaly, cholelithiasis, and calvarial vault thickening. Pediatricians in Korea must acknowledge thalassemia as a possible diagnosis in children with microcytic hypochromic hemolytic anemia. High level of suspicion will allow timely diagnosis and managements.

Identification of one or two α-globin gene deletions by isoelectric focusing electrophoresis

OBJECTIVES

To investigate the utility of isoelectric focusing electrophoresis (IEF) for identifying patients with α-thalassemia, which results from the deletion of 1 or more of the α-globin genes.

METHODS

Samples were selected based on their hemoglobin H (HbH) concentration observed using IEF. The samples were analyzed for the most common α-globin gene deletions using molecular analysis.

RESULTS

α-Globin gene deletions corresponding to α-thalassemia trait or silent carrier were observed in all samples with the HbH less than 2% phenotype. The genotypes of the specimens with HbH greater than 5% were consistent with HbH disease, while the wild-type phenotype control samples showed a wild-type genotype.

CONCLUSIONS

Low concentrations of HbH can be detected in a patient with 1 or 2 α-gene deletions using IEF.