Hb Hezhou [β64(E8)Gly→Ser; HBB: c.193G>A]: A Novel Variant on the β-Globin Gene

Early Onset of Severe Anemia Caused by Hb Calgary (HBB: C.194G > T): Another Case Report

Unstable hemoglobin (Hb) variants are a rare cause of congenital hemolytic anemia. We describe a Chinese girl who presented with transfusion-dependent anemia in early infancy. Her diagnosis of Hb Calgary [β64(E8)Gly > Val; HBB:c.194G > T] was not made until molecular testing was performed at the age of 5 years. Our case highlights the importance of early genetic testing in order to make the diagnosis, which may not only be useful for patient management and family counseling, but also for avoiding further unnecessary investigative attempts.

A novel mutation Hb jiangnan[β3(NA3) Leu→Lys, HBB:c.10-_11delinsAA] causing elevated Hb A2 level

OBJECTIVES

To report the hematolgocial and molecular features of a nove β-globin variant in a Chinese fimaly.

METHODS

The proband was a 19-year-old Chinese man whose Hb analysis by HPLC for thalassemia revealed an abnormal peak. Hb analysis was performed by HPLC and CE. Gap-PCR and PCR-reverse dot blot hybridization (PCR-RDB) were used to detect the common mutations in Chinese population. DNA sequencing was used to determine the Hb variant.

RESULTS

The Hb variant and Hb A can be separated but co-elutes with Hb F by the CE method. However, the variant can be separated from Hb A₀, Hb F, and Hb A₂ using HPLC. DNA sequencing showed a mutation of codon 3 in the β-globin gene. His wife's HPLC revealed a high value of Hb A₂, which proved to be the Hb E using PCR-RDB.

CONCLUSION

It was the first report of the mutation, so we named it Hb Jiangnan according to the place of residence of the proband. It can be separated by HPLC but not CE. Hb Jiangnan can cause an increased level of Hb A_2.

Hb Huadu [α124(H7)Ser→Thr (TCC>ACC), HBA2: c.373T>A]: A Novel Variant of the α-Globin Gene

Here, we report a novel α chain hemoglobin (Hb) variant found during routine thalassemia screening. This Hb variant can be detected by capillary electrophoresis (CE) but cannot be recognized by high performance liquid chromatography (HPLC). Sanger sequencing revealed a heterozygous missense substitution at nucleotide 373 on the HBA2 gene, which results in the replacement of serine by threonine at codon 124 [α124(H7)Ser→Thr (TCC>ACC), HBA2: c.373T>A]. It is the first report of this variant, named Hb Huadu for the birthplace of the proband. In addition, the proband coinherited the heterozygous codons 41/42 (-TTCT) (HBB: c126_129delCTTT) on the β-globin gene.

Hb Laibin [β96(FG3)Leu→Arg; HBB: c.290T>G]: A Novel Hemoglobin Variant Described in a Chinese Family

We report a novel β chain hemoglobin (Hb) variant found in a Chinese family. A high level of Hb F was observed on capillary electrophoresis (CE). However, high performance liquid chromatography (HPLC) showed a high level of Hb A₂. DNA sequencing revealed a single base substitution (T>G) at codon 96 of exon 2 of the β-globin gene. This alters the normally encoded leucine to arginine [β96(FG3)Leu→Arg; HBB: c.290T>G] that we propose to name Hb Laibin for the region of origin of the proband. The pedigree study showed that it was inherited from his mother.

Detection of Hb Yulin [β13(A10)Ala→Val, HBB: c.41C>T] by Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry

We report a rare hemoglobin (Hb) variant on the β-globin gene, which was detected in a female from Yulin City, Guangxi Autonomous Region, People's Republic of China (PRC), during routine thalassemia screening. The Hb variant remained unnoticed using capillary electrophoresis (CE) and high performance liquid chromatography (HPLC), while an additional peak was observed by matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry (MS). DNA sequencing revealed the GCC>GTC substitution at codon 13 on the β-globin gene, causing a substitution of alanine to valine. The mutation is only described in the ITHANET database but no Hb variant name and other information, so we named it Hb Yulin after the place of origin of the proband in this study. Hb Yulin is clinically silent and easily leads to misdiagnosis during hemoglobinopathies screening based on the common methods of HPLC and CE.

The value of single-molecule real-time technology in the diagnosis of rare thalassemia variants and analysis of phenotype-genotype correlation

To compare single-molecule real-time technology (SMRT) and conventional genetic diagnostic technology of rare types of thalassemia mutations, and to analyze the molecular characteristics and phenotypes of rare thalassemia gene variants, we used 434 cases with positive hematology screening as the cohort, then used SMRT technology and conventional gene diagnosis technology [(Gap-PCR, multiple ligation probe amplification technology (MLPA), PCR-reverse dot blot (RDB)] for thalassemia gene screening. Among the 434 enrolled cases, conventional technology identified 318 patients with variants (73.27%) and 116 patients without variants (26.73%), SMRT identified 361 patients with variants (83.18%), and 73 patients without variants (16.82%). The positive detection rate of SMRT was 9.91% higher than conventional technology. Combination of the two methods identified 485 positive alleles among 49 types of variant. The genotypes of 354 cases were concordant between the two methods, while 80 cases were discordant. Among the 80 cases, 76 cases had variants only identified in SMRT method, 3 cases had variants only identified in conventional method, and 1 false positive result by the traditional PCR detection technology. Except the three variants in HS40 and HBG1-HBG2 loci, which was beyond the design of SMRT method in this study, all the other discordant variants identified by SMRT were validated by further Sanger sequencing or MLPA. The hematological phenotypic parameters of 80 discordant cases were also analyzed. SMRT technology increased the positive detection rate of thalassemia genes, and detected rare thalassemia cases with variable phenotypes, which had great significance for clinical thalassemia gene screening.

Hb Dahua [β59(E3)Lys→Met; HBB: c.179A>T] a Novel Variant on the β-Globin Gene

We report a novel hemoglobin (Hb) variant found in a Chinese individual from the Guangxi Zhuang Autonomous Region of the People's Republic of China. The proband was a 6-month-old boy who came from Dahua county, Hechi City. Capillary zone electrophoresis (CZE) showed an abnormal peak (51.2%) in zone 13. However, capillary isoelectric focusing electrophoresis (CIFE) presented an unknown peak in zone Bart's (51.4%). High performance liquid chromatography (HPLC) displayed an unknown peak (42.1%) at retention time 2.44 min., eluting before Hb A₀. Direct DNA sequencing of the β-globin gene revealed heterozygosity for a missense mutation at codon 59 (AAG>ATG), causing a lysine to methionine substitution [β59(E3)Lys→Met; HBB: c.179A>T]. We decided to name the variant Hb Dahua for the place of origin of the proband.

Hb Calgary (HBB: c.194G>T): A Highly Unstable Hemoglobin Variant with a β-Thalassemia Major Phenotype

We describe two unrelated patients, both heterozygous for an unstable hemoglobin (Hb) variant named Hb Calgary (HBB: c.194G>T) that causes severe hemolytic anemia and dyserythorpoietic, resulting in transfusion dependence and iron overload. The molecular pathogenesis is a missense variation on the β-globin gene, presumed to lead to an unstable Hb. The phenotype of Hb Calgary is particularly severe presenting as transfusion-dependent anemia in early infancy, precluding phenotypic diagnosis and highlighting the importance of early genetic testing in order to make an accurate diagnosis.