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

OBJECTIVE: 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. MATERIALS AND METHODS: 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 ß-thal. RESULTS: 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 ß-thal behaved as ß-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 ß-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. CONCLUSION: 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.

[Association Analysis between Genotype and Phenotype of α,ß-Thalassaemia Carriers in Huizhou Area of Guangdong Province].

OBJECTIVE: To analyze the prevalence, genotype distribution and hematological characteristics of α,ß-thalassaemia carriers in Huizhou area of Guangdong Province. METHODS: 10 809 carriers of simple ß-thalassaemia and 1 757 carriers of α,ß-thalassaemia were enrolled as our study cohort. The hematological parameters were detected by automated blood cell counters and automatic capillary electrophoresis. Suspension array technology, gap-polymerase chain reaction (gap-PCR) and PCR-reverse dot blot were used for the genotyping of thalassaemia carriers. RESULTS: The prevalence of α,ß-thalassaemia in Huizhou area of Guangdong Province was 1.99%. A total of 62 genotypes were detected, and the most prevalent genotype was --SEA/ αα, ßCD41-42/ ßN (19.29%), the next was --SEA/ αα, ßIVS-II-654/ ßN (16.73%). Significant differences in mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) were found between different genotype groups for simple ß-thalassaemia and α,ß-thalassaemia. Violin plots showed that carriers with co-inheritance of ß-thalassaemia and mild α-thalassaemia expressed the lightest anemia, and carriers with co-inheritance of ß-thalassaemia and hemoglobin H (Hb H) disease expressed the most severe anemia. CONCLUSION: There is a high prevalence of α,ß-thalassaemia in Huizhou area of Guangdong Province. Because of the lack of specific hematological makers for diagnosis of α,ß-thalassaemia, it is necessary to distinguish it from simple ß-thalassaemia by genotyping of α- and ß-thalassaemia in order to correctly guide genetic counseling and prenatal disgnosis.

Case Report: The third-generation sequencing confirmed a novel 7.2 Kb deletion at ß-globin gene in a patient with rare ß-thalassemia.

Background: Thalassemia was the most common monogenic diseases worldwide, which was caused by mutations, deletions or duplications in human globin genes which disturbed the synthesis balance between α- and ß-globin chains of hemoglobin. There were many classics methods to diagnose thalassemia, but all of them had limitations. Although variations in the human ß-globin gene cluster were mainly point mutations, novel large deletions had been described in recent years along with the development of DNA sequencing technology. Case report: We present a case of 32-year-old male with abnormal hematological results. However, 23 genotypes of the most common thalassemia were not detected by two independent conventional platforms. Finally, using multiplex ligation-dependent probe amplification (MLPA), third-generation sequencing (TGS) and Gap PCR detection methods, we first confirmed the case with a novel 7.2 Kb deletion (Chr11:5222800-5230034, hg38) located at HBB gene. Conclusion: Our results showed that TGS technology was a powerful tool for thalassemia breakpoint detection, had promising potentiality in genetic screening of novel thalassemia, especially for the novel deletions in globin genes.

A novel 15.8 kb deletion α-thalassemia confirmed by long-read single-molecule real-time sequencing: Hematological phenotypes and molecular characterization.

BACKGROUND: Thalassemia is the most frequent recessive Mendelian inherited monogenic disease worldwide, and is characterized by the impaired synthesis of globin chains due to disease-causing variants in α- or ß-globin genes. There are many conventional methods to diagnose thalassemia but all of them have limitations. CASE REPORT: We present the case of a 37-year-old female with abnormal values of routine hematological indices who was admitted for genetic screening of thalassemia. Genomic DNA was extracted and used for genetic assays covering the known and potential novel genotypes in HBA and HBB genes using a suspension-array system, gap-polymerase chain reaction (Gap-PCR), PCR-reverse dot blot (PCR-RDB) and multiplex ligation-dependent probe amplification (MLPA). Finally, using long-read single-molecule real-time (SMRT) sequencing, we first confirmed the case with a novel 15.8 kb deletion located in the HBA gene (Chr16:163886-179768, GRch38/hg38). CONCLUSIONS: Our results showed that long-read SMRT sequencing has great advantages in the detection of rare α-globin gene variants. This study may provide a reference protocol for the use of long-read SMRT sequencing for the detection of known and potential novel genotypes of thalassemia in the population and improve the accuracy of genetic counseling and prenatal diagnosis.

A Case of Misdiagnosis Caused by the Coinheritance of Hb G-Siriraj [ß7(A4)Glu→Lys; HBB: c.22G>A] and Hb H Disease.

Despite the fact that most hemoglobin (Hb) variants are clinically and hematologically silent, they can interact with thalassemias, which could sometimes give rise to complicated routine thalassemia diagnostics. Hb G-Siriraj [ß7(A4)Glu→Lys; HBB: c.22G>A] alone is a benign condition, but its coinheritance with α-thalassemia (α-thal) may lead to misdiagnosis. We describe the case of a Chinese woman with an elevated Hb A2 level who was assumed to carry heterozygous ß-thalassemia (ß-thal), but was later shown to be a double heterozygote for Hb G-Siriraj and Hb H disease. This study for the first time described hematological characteristics of a patient with a double heterozygosity for Hb G-Siriraj and Hb H disease. It is of great significance for technicians and clinicians to expand their knowledge as well as to help guide clinical diagnosis, population screening and genetic counseling.

Genetic counseling and prenatal decision for hemoglobin H disease caused by the rare α2 codon 30 (-GAG) (HBA2: c.91_93delGAG) mutation and the SEA deletion: Case series study.

OBJECTIVE: We report a rare mutation on the α2-globin gene, HBA2: c.91_93delGAG and its potential functions. CASE REPORT: We mainly described four patients with hemoglobin (Hb) H disease caused by the rare mutation and the SEA deletion but diversity in clinical presentation. Two had survived to adulthood with normal physical and mental development, except for mild anemia. However, two were children, who had more severe clinical manifestations. One child had developmental disorders of speech and language and mild growth retardation, and the other child suffered from severe hemolytic crises precipitated by infection and received blood transfusion. CONCLUSION: This study is of great significance for clinicians to provide genetic counseling to couples at-risk of having offspring with Hb H disease and let them make the pregnancy decision, particularly reduce the occurrence of severe Hb H disease.

[Diagnosis and clinical phenotype analysis of a case with large fragment homozygous deletion of rare ß gene cluster].

OBJECTIVE: To report on a case with homozygous deletion of large ß gene cluster and its clinical characteristics. METHODS: A total of 71 001 peripheral blood samples were subjected to capillary electrophoresis and conventional testing for common thalassemia mutations. The genotypes of suspected ß gene cluster deletions were analyzed by Gap-PCR and multiplex ligation-dependent probe amplification (MLPA). Their hematological characteristics were compared by statistical analysis R software. RESULTS: Eighty-nine cases were detected with Chinese Gγ(Aγδß) 0-deletion of the ß gene cluster, which gave a detection rate of 0.13%. Among these, there were 70 Chinese Gγ(Aγδß) 0-deletion heterozygotes and 18 Chinese Gγ(Aγδß) 0-deletion heterozygotes in conjunct with α thalassemia. There were 13 683 samples with normal findings. A significant difference was detected in 6 groups of hematological parameters between the heterozygous carriers (P<0.05) by box plotting. One case of Chinese Gγ(Aγδß) 0-deletion homozygote was discovered for the first time. The clinical phenotype was mild anemia. Hemoglobin electrophoresis showed that the value of HbF was 100%. CONCLUSION: The carrier rate for large fragment deletions of ß gene cluster in Huizhou region is rather high, for which the value of HbF is significantly increased. Attention should be paid to screening and diagnosis of rare genotype to prevent missed diagnosis and/or misdiagnosis.

[Phenotypic and genotypic analysis of 45 cases with Hemoglobin Q-Thailand].

OBJECTIVE: To explore hematological and molecular characteristics of Hemoglobin Q-Thailand in Huizhou area of Guangdong Province. METHODS: A total of 34 977 samples were screened by capillary and agarose gel electrophoresis. Samples suspected with HbQ strips were subjected to blood cell count and DNA sequencing. Twenty three common mutations associated with α- and ß-thalassemia were identified by liquid phase chip and diversion hybridization technique. RESULTS: The carrier rate of Hb Q-Thailand in Huizhou area was 0.13%. Pedigree analysis indicated that the Hb Q-Thailand allele is linked with a leftward single a-globin gene deletion (-α4.2). Hematological index (HGB, MCV, MCH, HbA, HbA2, HbQ) of 45 heterozygous carriers of Hb Q-Thailand were (130.25±17.37) g/L, (79.81±4.97) fl, (26.38±1.48) pg, (71.37±5.07)%, (1.65±0.45)%, (26.87±4.95)%, respectively. A statistical difference was also found in their hematological index of HbA and HbA2 compared with 408 heterozygous carriers of -α4.2 mutation (P<0.05). CONCLUSION: Hb Q-Thailand has a high detection rate in Huizhou area. The allele is mainly in a heterozygous status and linked with -α4.2. The Hb Q strip can be detected by hemoglobin electrophoresis. When combined with other types of thalassemia, the heterozygotes will show unique hematological parameters.