β-Globin chain abnormalities with coexisting α-thalassemia mutations

Analysis of genotype-phenotype correlation in patients with α-thalassemia from Fujian province, Southeastern China

Background

There is a high carrying rate of α‐thalassemia in Fujian province. However, there are few large‐scale studies on the correlation between genotype and phenotype in Fujian province. The purpose of this study was to analyze the phenotype and genotype in a cohort of 2923 patients with α‐thalassemia in Fujian province, so as to provide reference data for screening and diagnosis of α‐thalassemia in Fujian province.

Methods

The genotype of α‐thalassemia was detected by PCR reverse dot blot assay, gap‐PCR, single PCR, nested PCR, and sequencing. Clinical and hematological indices of 2923 patients were collected, and the correlation between genotype and phenotype was analyzed.

Results

Among 10,350 patients, 2923 cases were found with α‐thalassemia, with a detection rate of 28.24%. Among them, ‐‐^SEA/αα was the most common genotype, accounting for 64.80%. In addition, rare α‐thalassemia genotypes were detected in Fujian province, including ‐‐^THAI/αα (0.41%), HKαα/‐‐^SEA (0.03%), and the novel α‐thalassemia gene mutation CD5 (GCC>ACC) (HGVS named HBA1: c.16G>A) (0.03%). Patients with deletional genotypes of α‐thalassemia were found to have higher RBC and lower Hb, MCV, MCH, and HbA2 than patients with non‐deletional genotypes of α‐thalassemia (p < 0.05).

Conclusion

The clinical phenotype of α‐thalassemia is influenced by molecular mechanisms. HBA1: c.16G>A mutation is a novel mutation that was first reported in Fujian province, which enriches the human hemoglobin mutation spectrum.

Combined Gap-Polymerase Chain Reaction and Targeted Next-Generation Sequencing Improve α- and β-Thalassemia Carrier Screening in Pregnant Women in Vietnam

Vietnam has a high thalassemia burden. We collected blood samples from 5880 pregnant Vietnamese women during prenatal health checks to assess thalassemia carrier frequency using combined gap-polymerase chain reaction (gap-PCR) and targeted next-generation sequencing (NGS). Thalassemia carriers were identified with prevalence of 13.13% (772), including 7.82% (460) carriers of α-thalassemia (α-thal), 5.31% (312) carriers of β-thalassemia (β-thal), and 0.63% (37) concurrent α-/β-thal carriers. Deletional mutations (368) accounted for 80.0% of α-thal carriers, of which, --^SEA (Southeast Asian) (n = 254; 55.0%) was most prevalent, followed by the -α^3.7 (rightward) (n = 66; 14.0%) and -α^4.2 (leftward) (n = 45; 9.8%) deletions. Hb Westmead (HBA2: c.369C>G) (n = 53) and Hb Constant Spring (Hb CS or HBA2: c.427T>C) (in 28) are the two most common nondeletional α-globin variants, accounting for 11.5 and 6.0% of α-thal carriers. We detected 11 different β-thal genotypes. Hb E (HBB: c.79G>A) (in 211) accounted for 67.6% of β-thal carriers. The most common β-thal genotypes were associated with mutations at codon 17 (A>T) (HBB: c.52A>T), codons 41/42 (-TTCT) (HBB: c.126_129delCTTT), and codon 71/72 (+A) (HBB: c.217_218insA) (prevalence 0.70%, 0.68%, and 0.2%, respectively). Based on mutation frequencies calculated in this study, estimates of 5021 babies in Vietnam are affected with clinically severe thalassemia annually. Our data suggest a higher thalassemia carrier frequency in Vietnam than previously reported. We established that combining NGS with gap-PCR creates an effective large-scale thalassemia screening method that can detect a broad range of mutations.

Etiologies, Cerebral Vasomotion, and Endothelial Dysfunction in the Pathophysiology of Posterior Reversible Encephalopathy Syndrome in Pediatric Patients

The posterior reversible encephalopathy syndrome was characterized by Hinchey and colleagues in the 1990s. The condition frequently afflicts patients suffering from hematologic and solid organ malignancy and individuals undergoing transplantation. Cases are more frequently described in the adult population compared with children. In the pediatric population, malignancy, transplantation, renal disease, and hypertension represent the most common etiologies. Theories on pathogenesis have centered upon cerebrovascular dysautoregulation with increases in blood–brain barrier permeability. This generates vasogenic edema of the cerebral parenchyma and consequent neurologic deficits. The parietal and occipital lobes are affected with greatest prevalence, though frontal and temporal lobe involvement is frequent, and that of the contents of the infratentorial posterior cranial fossa are occasionally described. The clinical presentation involves a characteristic constellation of neurologic signs and symptoms, most typically inclusive of headache, visual-field disturbances, abnormalities of visual acuity, and seizures. Supportive care, withdrawal of the offending agent, antihypertensive therapy, and prophylactic anticonvulsants affect convalescence in majority of cases. The principal challenge lies in identifying the responsible agent precipitating the condition in patients with malignancy and those having undergone transplantation and thus deciding which medication among a multidrug treatment regimen to withhold, the duration of drug cessation required to effect clinical resolution, and the safety of resuming treatment with the compound. We accordingly reviewed and evaluated the literature discussing the posterior reversible encephalopathy syndrome in children.

Molecular characterization of thalassemia and hemoglobinopathy in Southeastern China

Thalassemia and hemoglobinopathy are two common inherited disorders, which are highly prevalent in southern China. However, there is little knowledge on the genotypes of thalassemia and hemoglobinopathy in Southeastern China. In this study, we present a large-scale genetic detection and molecular characterization of thalassemia and hemoglobinopathy in Fujian province, Southeastern China. A total of 189414 subjects screened for thalassemia were recruited, and the hemoglobin components and levels were investigated. Furthermore, suspected common thalassemia was identified, and the suspected rare forms of common thalassemias and hemoglobinopathy were detected. Among the total subjects screened, the overall prevalence of thalassemia and hemoglobinopathy was 6.8% and 0.26%, and rare α-thalassemia genotypes HKαα, –^THAI/αα and −α^27.6/αα, and novel β-thalassemia gene mutations CD90(G → T) and IVS-I-110(G > A) were identified. Additionally, Hb Q-Thailand hemoglobinopathy and five other types of hemoglobinopathies (Hb New York, Hb J-Bangkok, Hb G-Taipei, Hb G-Coushatta and Hb Maputo) were found. The results of this 10-year large-scale study demonstrate high prevalence of thalassemia with complicated gene mutations in Southeastern China, which provides valuable baseline data for genetic counseling and prenatal diagnosis. In addition to detection of common thalassemia genes, detection of rare thalassemia genotypes and hemoglobinopathies is recommended.

KLF1 gene and borderline hemoglobin A2 in Saudi population

INTRODUCTION

Elevated HbA₂ (hemoglobin A₂) level is considered the most reliable hematological parameter for the detection of β-thalassemia carriers. However, some carriers are difficult to recognize because the level of HbA₂ is not in the distinctive carrier range, i.e. 4.0-6.0%; instead, some carriers have HbA₂ levels between normal and carrier levels, i.e. borderline HbA₂ (HbA₂ = 3.1-3.9%). Studies have shown that variations in the erythroid Krüppel-like factor (KLF1) gene lead to borderline HbA₂ in β-thalassemia carriers from various populations. The incidence of borderline HbA₂ in Saudis is high.

MATERIAL AND METHODS

To confirm the influence of variations in KLF1, HBA1, HBA2 and HBB genes for the reduction of the level of HbA₂ in Saudi β-thalassemia carriers, we performed a direct sequence analysis of KLF1, HBA1, HBA2 and HBB genes from 212 healthy Saudis (88 subjects: HbA₂ < 3; 72 subjects: HbA₂ = 3.1 to 3.9; 52 subjects HbA₂ > 4.3).

RESULTS

The presence of the borderline HbA₂ level is not specific to any type of β-thalassemia variation or β⁺-thalassemia variations in Saudis. Two exonic (c.304T>C and c.544T>C) and two 3' untranslated region (3'UTR) (c.*296G>A and c.*277C>G) variations have been identified in the KLF1 gene for the first time from an Arab population. None of these four variations in KLF1 genes are significantly associated with the Saudis with borderline HbA₂. α Globin genotype, -α₂^3.7/α₁α₂, is found to be the most frequent (55.55%) among healthy Saudis with borderline HbA₂ compared with the other groups (HbA₂ < 3 = 20.45%; HbA₂ > 4.3 = 13.51%).

CONCLUSIONS

Further studies are necessary to determine the influence of other factors on the presence of borderline HbA₂ in 41.67% of Saudis.

Laboratory parameters provided by Advia 2120 analyser identify structural haemoglobinopathy carriers and discriminate between Hb S trait and Hb C trait

BACKGROUND

Haemoglobinopathies have spread owing to human migration, and the number of people needing diagnosis and management of these conditions is increasing. Clinicians need to accurately identify carriers and provide adequate genetic counselling in order to prevent the occurrence of homozygous or compound heterozygous offspring.

OBJECTIVES

To identify red blood cell (RBC) laboratory parameters that discriminate between structural haemoglobinopathy carriers and healthy subjects, and to compare RBC laboratory indices between HbAS and HbAC individuals.

METHODS

Samples of 500 variant Hb carriers (355 HbAS, 104 HbAC, 19 HbAD, 7 HbAE, 7 HbAO-Arab, 4 α-chain variants and 4 Hb Lepore) and 251 normal controls were run on an Advia 2120 analyser (Siemens). Classic haematological parameters and RBC populations were assessed in all subjects. A multivariable binary logistic regression model was created to predict the probability of a subject carrying any structural haemoglobinopathy. HbAS (n=355, 71%) and HbAC (n=104, 20.8%) subjects were compared.

RESULTS

A clinical prediction rule was developed by assigning one point to each of the most efficient variables: mean corpuscular volume (MCV) <88.4 fL, RBC distribution width >13.4%, percentage of microcytic RBCs (%MICRO) >0.7% and the ratio of microcytic RBCs to hypochromic RBCs >0.8. A score of 0, 1, 2, 3 or 4, resulted in a probability of 9.6%, 36.3%, 66.7%, 85.2% or 98.3%, respectively. Among the most frequent variant Hb, HbAC subjects had lower values of parameters related to cell size (MCV, %MICRO) and higher values of parameters related to haemoglobin concentration (MCHC, %HYPER) than HbAS subjects. Coexistence of α-thalassaemia in both HbAS and HbAC individuals resulted in decreased Hb, MCV, MCH and MCHC.

CONCLUSIONS

Structural haemoglobinopathy should be investigated in subjects belonging to ethnic groups with high prevalence of variant Hb and with a score of 3 or 4. Erythrocytes of HbAC subjects are smaller and denser than those of HbAS subjects.

Hepatitis B, Hepatitis C, Human immunodeficiency virus and syphilis frequency among blood donors: A single center study

We aimed to provide updated results for seroprevalence of hepatitis B, hepatitis C viruses while presenting first data for human immunodeficiency virus and syphilis seropositivity amongst blood donors in Adana, Turkey. Screening and confirmatory test results of 62,461 donors were evaluated. HBsAg, anti-HCV, anti-HIV1/2 and syphilis seropositivity was 1.92%, 0.48%, 0.20%, 0.18% respectively, based on screening tests, and 1.66%, 0.05%, 0.003%, 0.10% respectively, according to confirmatory tests. Transfusion-transmitted infections (TTI) was more prevalent in low-educated donors. HBsAg and syphilis seropositivity rates were higher in married subjects. We found that the prevalence of HBV and HCV was significantly decreased in the last two decades in Adana. Importantly, this study provides first data in HIV and syphilis seropositivity rates among blood donors in our region and both HIV and syphilis seroprevalences were found to be low compared to many regions of Turkey. However, considering the fact that increasing number of immigrants may change prevalences and trends of TTI both in Adana and in Turkey, strict monitorization and yearly reporting of TTI rates seem necessary to be able to take proactive measures.

Molecular spectrum of α-globin gene mutations in the Aegean region of Turkey: first observation of three α-globin gene mutations in the Turkish population

Molecular test results of 231 individuals referred to our molecular genetics laboratory for analysis of α-globin gene mutations between the years 2007 and 2013 were evaluated. Analysis of α-thalassemia gene mutations was performed using reverse dot-blot hybridisation, which includes 21 common mutations. Twelve distinct α-thalassemia mutations and 23 different genotypes have been detected in the Aegean region of Turkey. The most frequent mutations were -α3.7 (52.28 %), -(α)20.5 (14.74 %), --MED (10.53 %), and αPA-1α (8.77 %). Three α-thalassemia mutations (αcd142α, --SEA, and αICα), which are more prevalent in Southeast Asia, are identified for the first time in Turkey in this study. We find that a broad spectrum of α-thalassemia mutations is present in the Aegean region of Turkey. The results obtained in this study may help inform decisions in the design and implementation of prevention strategies and diagnostic approaches.