Hb H disease associated with compound heterozygosity for --SEA deletion and a novel alpha globin chain variant (HBA2:c.175C>A) on the distal histidine in a Chinese family

OBJECTIVES

In clinical practice, the majority of α-thalassaemia cases arise from deletions of the α-globin genes. However, a subset of cases is attributed to rare haemoglobin variants, which can manifest with borderline or normal screening results, potentially leading to missed diagnoses in clinical practice.

METHODS

Blood samples were collected from family members and underwent haematological, DNA and RNA analysis.

RESULTS

The five-month-old proband presented a haematological phenotype consistent with Hb H disease. The mother's haematology profile was consistent with an α-thalassaemia carrier, while the father exhibited a borderline reduction in MCV and MCH. MALDI-TOF identified an abnormal α-chain in the proband. DNA analysis revealed a novel α-globin variant (HBA2:c.175C>A, α58His>Asn, Hb DG-Nancheng) affecting the distal histidine in the family. The father and the mother had α-genotype of --SEA/αα and αDG-Nanchengα/αα, respectively; while the proband inherited both mutant alleles (--SEA/αDG-Nanchengα). Sequencing of cDNA from HBA2 gene identified an equal ratio of normal and mutant alleles.

CONCLUSION

This rare case highlighted the importance of identifying rare haemoglobin variant during prenatal screening. The clinical and genetic data provides useful information on the pathogenicity of this variant and further insight into the role of distal histidine residue of α-globin.

Thrombosis Tendency After Splenectomy in a Danish Family With Hemoglobin Volga, and a Literature Review

Hemoglobin (Hb) Volga is a rare, unstable β-chain hemoglobin variant (β27 Ala→Asp), causing chronic hemolytic anemia. This study presents two members of a Danish family, splenectomized due to Hb Volga at and with multiple thrombotic events. The proband was diagnosed with Hb Volga 9 years old and splenectomy was performed as a part of treatment. Throughout his life, he experienced multiple superficial thrombophlebitis, two episodes of distal deep venous thrombosis (DVT) on lower extremities (age 32 and 33) and a transient ischemic attack (TIA) presented as amaurosis fugax (age 51). Thrombophilia investigation was normal. The proband's son was diagnosed with Hb Volga and underwent splenectomy at the age of 6. Despite anticoagulation therapy, he suffered from multiple venous thromboembolic events in his youth and died of chronic pulmonary embolism (PE)/pulmonary hypertension combined with infection. Given the observed propensity for multiple thromboses in these two patients, a literature review was conducted investigating reported occurrence of thrombotic events in individuals with Hb Volga.

Currently 25 cases of Hb Volga are reported worldwide. The clinical symptoms primarily described are related to hemolytic anemia. Splenectomy is reported in 15 patients. Thromboses have previously been reported in only three patients who were also splenectomized. These cases involved DVT and PE, myocardial infarction, and an unspecified thrombotic event. The proband represents the first reported Hb Volga case with both venous and arterial thrombotic disorders. The exact mechanism underlying thrombotic tendency in patients with Hb Volga remains unknown, but it is probably associated with splenectomy.

Uncommon causes of hemoglobin E flags identified during measurement of hemoglobin A1c by ion-exchange high-performance liquid chromatography

We present 3 cases of discordant results from screening hemoglobin A1c (HbA1c) measured by ion-exchange high-performance liquid chromatography (HPLC) all due to various forms of interference and flagged by the instrument as "suspected hemoglobin E (HbE)." The first case was due to a rare hemoglobin variant, later confirmed to be hemoglobin Hoshida, the second due to "true" heterozygous HbE, and the third a result of analytical artifact causing splitting of the HbA1c peak without an underlying variant hemoglobin. We examine the similarities in these cases along with the laboratory work-up to classify each cause of interference to demonstrate the wide array of potential causes for the suspected HbE flag and why it warrants proper work-up. Because there is no standardized method of reporting out hemoglobin variant interference in HbA1c measurement, we discuss our laboratory's process of investigating discordant HbA1c measurements and reporting results in cases with variant interference as 1 possible model to follow, along with discussing the associated laboratory, ethical, and clinical considerations. We also examine the structure of hemoglobin Hoshida, HbE, and conduct a brief literature review of previous reports.

Mutational spectrum of HBD gene in the Chinese population: Description of 36 mutations including 11 novel variants

INTRODUCTION

Mutations in the hemoglobin subunit delta (HBD) gene (MIM#142000) are associated with decreased levels of the Hemoglobin A2 (Hb A2 ) fraction. We aimed to examine the prevalence of HBD gene mutations and summarize their characteristics in the Chinese population.

METHODS

Individuals who exhibited Hb A2 levels below 1.8%, with or without Hb A2 variant peaks, were chosen for further investigation. Hemoglobin analysis was conducted using capillary electrophoresis. Common α and β-thalassemia in China were detected using gap-PCR and reverse dot blot hybridization. The presence of HBD gene mutations was confirmed by DNA sequencing.

RESULTS

A total of 188 patients were identified as carriers of the HBD gene mutation, with a prevalence of approximately 0.46%. We discovered 36 types of mutations, 30 of which resulted in δ-globin variants, while the remaining 6 resulted in δ-thalassemia. The most common mutation was HBD:c.-127 T > C, accounting for 87.2% of δ-thalassemia cases. In addition, we identified 11 novel HBD gene mutations and found 10 cases compounded with other common thalassemias.

CONCLUSION

We observed a high prevalence of HBD gene mutations in southern China. Our findings provide a genetic basis for screening for δ-thalassemia and enrich the spectrum of HBD gene mutations.

Hb Chapel Hill or Alpha2 74(EF3) Asp>Gly, a mildly unstable variant found in a Chinese family

BACKGROUND

Hb Chapel Hill [Alpha2 74(EF3) Asp > Gly] results from an GAC > GGC substitution at codon 74 of the HBA1 or HBA2 genes. Hb Chapel Hill has not been reported since 1986.

METHODS

A heterozygous mutation, HBA2: c.224A > G, was identified in the proband, her father and sister. We compared the haematological and clinical data of this family with the data reported in the limited number of individuals.

RESULTS

Having excluded iron deficiency, the Hb Chapel Hill was asymptomatic in heterozygous state. The cases presented here characterize cases in new techniques including capillary electrophoresis (CE). Two aberrant peaks were identified by CE, a major peak migrating in the zone 7 that correspond to Hb Chapel Hill (αChapel Hill 2β2) and a minor peak migrating in the zone 1 that correspond to Hb Chapel Hill2 (αChapel Hill 2δ2). Focusing on the variant expression, the Hb Chapel Hill plus Hb A2 variant were around 18.9-20.6% of total Hb in three members.

CONCLUSION

This data will be useful for providing up-to-date and high quality information on the Hb Chapel Hill.

Hb Q-Thailand heterozygosity unlinked with the (-α4.2/) α+-thalassemia deletion allele identified by long-read SMRT sequencing: hematological and molecular analyses

OBJECTIVE

In the present study, two unrelated cases of Hb Q-Thailand heterozygosity unlinked with the (-α^4.2/) α⁺-thalassemia deletion allele were identified by long-read single molecule real-time (SMRT) sequencing in southern China. The aim of this study was to report the hematological and molecular features as well as diagnostic aspects of the rare manifestation.

METHODS

Hematological parameters and hemoglobin analysis results were recorded. A suspension array system for routine thalassemia genetic analysis and long-read SMRT sequencing were applied in parallel for thalassemia genotyping. Traditional methods, including Sanger sequencing, multiplex gap-polymerase chain reaction (gap-PCR) and multiplex ligation-dependent probe amplification (MLPA), were used together to confirm the thalassemia variants.

RESULTS

Long-read SMRT sequencing was used to diagnose two Hb Q-Thailand heterozygous patients for whom the hemoglobin variant was unlinked to the (-α^4.2/) allele for the first time. The hitherto undescribed genotypes were verified by traditional methods. Hematological parameters were compared with those of Hb Q-Thailand heterozygosity linked with the (-α^4.2/) deletion allele in our study. For the positive control samples, long-read SMRT sequencing revealed a linkage relationship between the Hb Q-Thailand allele and the (-α^4.2/) deletion allele.

CONCLUSIONS

Identification of the two patients confirms that the linkage relationship between the Hb Q-Thailand allele and the (-α^4.2/) deletion allele is a common possibility but not a certainty. Remarkably, as it is superior to traditional methods, SMRT technology may eventually serve as a more comprehensive and precise method that holds promising prospects in clinical practice, especially for rare variants.

A Novel β-Globin Variant, Hb Raklev [β 75(E19) HBB:c.227T > A (Leu→Gln)]

We present a new hemoglobin variant, Hb Raklev, characterized by the substitution of leucine with glutamine at position 75 in the β-globin chain. This variant was discovered inadvertently during an HbA1c evaluation using high performance liquid chromatography in a symptomless 54-year-old Caucasian woman, with the same variant also identified in her 16-year-old daughter. Purification of the hemoglobin revealed possibly diminished 2,3-bisphosphoglycerate (2,3-BPG) sensitivity, which may result in heightened oxygen affinity. Notably, two variants have been previously documented at this location: the unstable Hb Atlanta and the high-affinity Hb Pasadena.

The pivotal role of HbA1c assay to detect hemoglobinopathies: A 5-year observational retrospective study in the population of Southern France

Background and Aims

Mobility and migration flows are growing from different countries of the world to European countries, including France and in particular the Mediterranean basin. This study aimed to investigate the presence of hemoglobin (Hb) variants in outpatients/inpatients of the Montpellier Hospital (France) in whom an HbA1c assay had been performed and for which the country of birth had been informed.

Methods

This is a retrospective study from January 2016 to December 2020 based on all high-performance liquid chromatography (HPLC) chromatograms (Tosoh Bioscience HLC-723G8) having an alarm of suspected Hb variant during HbA1c measurement. The corresponding samples were systematically sent to the hematology laboratory for confirmation and identification of Hb variant. Patient's medical history, clinical and demographic data were extracted from each medical chart. Statistical analyses were performed using XLSTAT® software, version 2016.06.35661.

Results

Three hundred sixty-three patients were confirmed with Hb variant exhibiting 17 different Hb profiles, highlighting the pivotal role of glycated hemoglobin (HbA1c) as a detection step. The prevalence of Hb variant in this southern French population was 0.71%, with the highest frequency for the beta-globin variants (n = 342/363; i.e., 94.2%), including the most common: S, C, E, and D in 200/342 (58.5%), 83/342 (24.3%), 29/342 (8.5%), and 11/342 (3.2%), respectively. Among patients with Hb variants, almost half (165/363; i.e., 45.4%) were born in the African continent with a predominance for Morocco (32/165; i.e., 19.3%) and Algeria (29/165; i.e., 17.5%).

Conclusion

HbA1c assay is a useful tool to detect Hb variants. Hemoglobinopathies are a public health issue in the current French population which is a multiethnic society. Despite the monocentric nature of our study, we note a high frequency of Hb variants in the south of France, which underlines the importance of screening for Hb variants in the whole population.

Evaluation of interference from 16 hemoglobin variants on hemoglobin A1c measurement by five methods

Hb variants prevalent in China are different from those in other countries. We aimed to assess the interference from Hb variants found in China on HbA1c measurement. All Hb variants were confirmed using Sanger sequencing. HbA1c was measured using a capillary electrophoresis method (Capillarys 3 OCTA), two cation-exchange high-performance liquid chromatography methods (ADAMS HA-8180V and HLC-723 G8 standard mode), an immunoassay (Cobas c501), and a boronate affinity chromatography method (Premier Hb9210). Premier Hb9210 was used as a comparative method. A total of 16 species of Hb variants were identified in 102 variant carriers. The most common variant was Hb E, followed by Hb Q-Thailand, Hb New York and Hb J-Bangkok. Clinically significant interference was observed for the Capillarys 3 OCTA (two Hb variants), ADAMS HA-8180V (seven Hb variants), HLC-723 G8 (14 Hb variants), and Cobas c501 (two Hb variants). The proportion of unacceptable HbA1c results was 13.7% for Capillarys 3 OCTA, 52.9% for HA-8180V, 83.3% for HLC-723 G8, and 3.9% for Cobas c501. Hb variants in China severely affect the accuracy of some commonly used HbA1c methods.

Identification of a rare compound heterozygous hemoglobin variant β0-thal [β17(A14) Lys>Stop, HBB: c.52A>T] and Hb J-Lome [β59(E3) Lys>Asn, HBB: c.180G>C]

BACKGROUND

HbA1c is the validated biomarker for glycemic management in diabetic individuals. Here, we report a compound heterozygote for β⁰-thal and Hb J-Lomeand evaluate its effect on HbA1c measurements.

METHODS

A 51-year-old female was suspected of harboring a hemoglobin variant following no value of HbA1c levelby Arkray HA-8180 V (48s HbA1c mode), abnormal hematological data, and abnormalhemoglobin analysison capillary electrophoresis (Capillarys 2 Flex Piercing, Hb program). Sanger sequencing of the α and β genes was subsequently performed on the proband.HbA1c was reanalyzed using D10 (Bio-Rad), Capillarys 2 Flex Piercing (Sebia), and Roche Cobas c501 (Roche Diagnostics).

RESULTS

Sanger sequencing identified a compound heterozygote for β⁰-thal [β17(A14) Lys > Stop, HBB: c.52A > T] and Hb J-Lome [β59(E3) Lys > Asn, HBB: c.180G > C].HbA1c values ⁣⁣determinedby D10, Capillarys 2 Flex Piercing (HbA1c program), and Roche Cobas c501were 2.3%, no HbA1c value, and 5.1 (32 mmol/mol), respectively. During pedigree analysis, the son of the proband was found to have normal blood glucose (5.55 mmol/L), decreased HbA1c (3.6%, 16 mmol/mol)by Arkray HA-8180 V (48s HbA1c mode), an abnormal band on the electrophoretogram of Capillarys2 (Hb program), and the Hb J-Lome mutation in the β globin gene.Subsequently, HbA1c values ⁣⁣determinedby D10, Capillarys 2 Flex Piercing (HbA1c program), and Roche Cobas c501 were4.0% (20 mmol/mol), no HbA1c value, and 5.0 (31 mmol/mol), respectively.

CONCLUSION

Atypically low HbA1c levels or a discrepancy between blood glucose and HbA1c levels should raise concerns about hemoglobin variations.

The first Chinese case of unstable Hemoglobin Santa Ana detected by capillary electrophoresis: a case report and literature review

Hemoglobin Santa Ana [β88(F4)Leu→Pro (CTG > CCG) HBB: c.266T > C] is an unstable hemoglobin variant characterized by a substitution of the amino acid leucine by proline at the 88th position of the β-globin chain. We for the first time identified this hemoglobin variant in a Chinese patient by capillary electrophoresis (CE). The proband was an 8-year-old boy with chronic anemia, brown urine and splenomegaly. He had been affected by moderate anemia, twice approaching a severe degree, that was attributed to infection. The CE result revealed an abnormal hemoglobin peak at electrophoretic zone 4 that correspond to the hemoglobin Santa Ana peak, and a CTG > CCG mutation at codon 88 of the β-globin gene was confirmed by DNA sequencing. To avoid misdiagnosis and genetic risks, a literature review of other unstable hemoglobins that migrate similarly to the hemoglobin Santa Ana was performed. Our findings indicate that hemoglobin Santa Ana can be clearly separated by CE, with accurate diagnosis depending on molecular analysis. This information will be useful for providing appropriate genetic counselling and for prenatal diagnosis.

[Anti-interference hemoglobin analysis system by high performance liquid chromatography]

High performance liquid chromatography (HPLC) is currently the mainstream technology for detecting hemoglobin. Glycated hemoglobin (HbA1c) is a gold indicator for diagnosing diabetes, however, the accuracy of HbA1c test is affected by thalassemia factor hemoglobin F (HbF)/hemoglobin A2 (HbA2) and variant hemoglobin during HPLC analysis. In this study, a new anti-interference hemoglobin analysis system of HPLC is proposed. In this system, the high-pressure three-gradient elution method was improved, and the particle size and sieve plate aperture in the high-pressure chromatography column and the structure of the double-plunger reciprocating series high-pressure pump were optimized. The system could diagnose both HbA1c and thalassemia factor HbF/HbA2 and variant hemoglobin, and the performance of the system was anti-interference and stable. It is expected to achieve industrialization. In this study, the HbA1c and thalassemia factor HbF/HbA2 detection performance was compared between this system and the world's first-line brand products such as Tosoh G8, Bio-Rad Ⅶ and D10 glycosylated hemoglobin analysis system. The results showed that the linear correlation between this system and the world-class system was good. The system is the first domestic hemoglobin analysis system by HPLC for screening of HbA1c and thalassemia factor HbF/HbA2 rapidly and accurately.

Misleading HbA1c Measurement in Diabetic Patients with Hemoglobin Variants

BACKGROUND AND OBJECTIVES

Hemoglobin A1c (HbA1c) is widely used for the monitoring and management of diabetes mellitus. The aim of this study is to investigate the influence of hemoglobin (Hb) variants on the measurement of HbA1c.

MATERIALS AND METHODS

HbA1c levels of 845 blood samples obtained from diabetic patients with various hemoglobin types were measured using a turbidimetric inhibition immunoassay and capillary electrophoresis.

RESULTS

Of 845 patients with diabetes, 65.7% (555/845) have the normal hemoglobin type (A₂A) and 34.3% (290/845) have various abnormal hemoglobin types, including heterozygous HbE 30.2% (255/845), homozygous HbE 1.9 % (16/845), Hb Constant Spring (CS) trait 1.4% (12/845), CSEA Bart's 0.2% (2/845), and beta-thalassemia trait 0.6% (5/845). In most of the patients with diabetes, HbA1c levels determined by two different methods, inhibition immunoassay and capillary electrophoresis, gave strong positive correlation (R = 0.901, P < 0.001), except for those with homozygous HbE (N = 16) and CSEA Bart's (N = 2). In all 18 patients with homozygous HbE and CSEA Bart's, the HbA1c was undetectable by capillary electrophoresis, meaning that their estimated average glucose was undeterminable, although their HbA1c levels could be measured using an inhibition immunoassay. The discrepancy of HbA1c results obtained from two different methods is noted in patients without HbA.

CONCLUSIONS

We have demonstrated the erroneous nature of HbA1c measurement in patients with hemoglobin variants, especially in those without HbA expression. Therefore, in the population with a high prevalence of hemoglobinopathies, hemoglobin typing should be considered as basic information prior to HbA1c measurement.

Spectrum of hemoglobin disorders in southern Odisha, India: a hospital based study

Background:

Hemoglobin disorders are the leading health concern in the world including India. There is a paucity of literature on the spectrum of hemoglobin disorders in southern districts of Odisha state. This study was undertaken to elucidate the occurrence of different hemoglobin disorders in a tertiary health care facility of Odisha state, India.

Methods:

The study cases were suspected patients of all age groups advised for screening of different hemoglobin disorders. Hemoglobin disorders were screened by sickling slide test and high-performance liquid chromatography (HPLC) using the Variant-II hemoglobin testing system as per the manufacturer's guidelines.

Results:

Over 2 years, 2332 blood samples (including 1102 pediatric and 1230 adult cases) were investigated, out of which, 1380 (59.2%) of cases had abnormal hemoglobin disorders. The most common was sickle cell disorders (48.67%, 1135/2332) followed by β-thalassemia (11.32%, 264/2332). Some rare variants were detected as hemoglobin D^-Punjab, hemoglobin E, hemoglobin Lepore, hereditary persistence of fetal hemoglobin, hemoglobin with high P2 window, hemoglobin with high P3 window etc, Among the cases with abnormal hemoglobin disorders, 744 (53.9%), 545 (39.5%) and, 91 (6.6%) cases were found to have the heterozygous, homozygous and, double heterozygous state. Of the 188 ante-natal cases screened, 31.4% of cases had abnormal hemoglobin variants with sickle cell disorders being the most prevalent one.

Conclusion:

Along with the high occurrence of sickle cell disorders in the study area, some other rare hemoglobin disorders are also prevalent which calls for a large community-based cohort study.

Compound heterozygosity for hemoglobin variant Hb-Broomhill and the Southeast Asian α-thalassemia deletion does not worsen outcome: a case report of two unrelated patients

We report two unrelated cases of compound heterozygosity for hemoglobin (Hb) variant Broomhill and the Southeast Asian (- - ^SEA/) α-thalassemia deletion, whose clinical features and laboratory findings have never been reported. Hematological analyses revealed abnormal values for both cases as α-thalassemia traits, and capillary electrophoresis suggested an abnormal peak that was incompletely separated from the Hb A peak. A suspension array system and Sanger sequencing were used to characterize the genotypes. Sanger sequencing confirmed the presence of Hb Broomhill [α114(GH2)Pro→Ala; HBA1: c.343C>G]. Eventually, both cases were accurately diagnosed as compound heterozygotes for Hb Broomhill and the (- - ^SEA/) α-thalassemia deletion, which is the first known report of these variants. This information will be useful when providing appropriate genetic counselling and prenatal diagnosis.

Evaluation on the separated effect of 13 hemoglobin variants by a new automatic Hba1c analyzer

Objective

To evaluate the effect of a new type of automatic glycated hemoglobin analyzer on the separation of abnormal hemoglobin.

Methods

Samples diagnosed as hemoglobin variants by capillary electrophoresis and gene testing were selected, and HbA1c analyzer was used for separation and detection.

Results

A total of 13 hemoglobin variants in 40 samples could be separated from the normal peaks.

Conclusions

The variant mode of hemoglobin HbA1c can identify a variety of hemoglobin variants, and the type of variants can be preliminarily determined according to the retention time and characteristic peak shape of the variants.

Hb broomhill [α1 or α2 114(GH2) pro > ala;HBA1 or HBA2:c.343C > G]: a rare Hb variant found in a diabetic chinese individual

We report a clinically silent hemoglobin (Hb) variant, Hb Broomhill [α1 or α2 114(GH2) Pro > Ala;HBA1 or HBA2:c.343C > G] in a diabetic Chinese man. The Hb fractions of the subject were analyzed using various chromatographic and electrophoretic techniques. The glycated hemoglobin (HbA1c) levels measured using cation-exchange high-performance liquid chromatography (CE-HPLC) and the boronate affinity method showed nearly identical results. Analysis of the chromatogram of the CE-HPLC revealed an abnormal shoulder peak that appeared towards the end of the elution profile. Though the capillary electrophoresis method did not interpret the results, a manual examination revealed an abnormal shoulder on the HbA0 peak. Similarly, the electropherogram of the capillary zone electrophoresis also had an abnormal shoulder on the HbA peak. A missense mutation specific to the Hb Broomhill variant was found using Sanger sequencing.

Hemoglobin variants in southern China: results obtained during the measurement of glycated hemoglobin in a large population

Objectives

Hemoglobin (Hb) variant is one of the most common monogenic inherited disorders. We aimed to explore the prevalence and hematological and molecular characteristics of Hb variants in southern China.

Methods

We collected blood samples from all patients with suspected variants found during HbA1c measurement via a cation-exchange high-performance liquid chromatography system (Bio-Rad Variant II Turbo 2.0) or a capillary electrophoresis method (Sebia Capillarys). Hematological analysis, Sanger sequencing, and gap-PCR were performed for these samples.

Results

Among the 311,024 patients tested, we found 1,074 Hb variant carriers, including 823 identified using Capillarys and 251 using Variant II Turbo 2.0, with a total carrier rate of 0.35%. We discovered 117 types of Hb variants (52 HBB, 47 HBA, and 18 HBD mutations) containing 18 new mutations. The most common variant found was Hb E, followed by Hb New York, Hb J-Bangkok, Hb Q-Thailand, Hb G-Coushatta, Hb G-Honolulu, Hb G-Taipei, and Hb Broomhill. Most heterozygotes for the Hb variant exhibited normal hematological parameters. However, most patients with compound heterozygotes for the Hb variant and thalassemia showed varied degrees of microcytic hypochromic anemia.

Conclusions

The prevalence of hemoglobin variants remains high and exhibits genetic diversity and widespread distribution in the population of southern China.

A Pitfall in HbA1c Testing Caused by Hb Long Island Hemoglobin Variant

BACKGROUND

Although many factors may interfere with hemoglobin (Hb)A1c measurement, Hb variants are among the most important factors.

METHODS

We tested the HbA1c levels of the patient, a 32 year old Manchu Chinese woman, during a routine health check. We used different methods, including high-performance liquid chromatography (HPLC) and capillary electrophoresis, to test specimens from the patient. Next, we tested the specimen further using polymerase chain reaction (PCR) and sequencing.

RESULTS

We discovered that our patient, who had an HbA1c value of 0, also has an Hb variant, Hb Long Island, which we found during the HbA1c analysis as part of her routine health check at the Health Management Center in the General Hospital of Tianjin Medical University, Tianjin, China. Also, we discovered that the exon 1 of β gene contained transversion mutations, with 1 heterozygous and 1 homozygous variant (HBB:c.8A > C, 9T > C). These gene mutations resulted in an amino-acid change (His to Pro) and a decrease in HbA1c value.

CONCLUSIONS

When there is no correlation between the clinical signs, glycemic status, and glycated Hb levels of the patient, the chromatogram of HbA1c should be carefully checked to detect possible variants that cause interference in the measurement.

Hb Sichuan [α67(E16)Thr→Ile, HBA2: c.203C>T]: A Novel Hemoglobin Variant That Can Be Detected by Glycated Hemoglobin Electrophoresis

We report a novel α2-globin chain hemoglobin (Hb) variant in a 23-year-old female of Chinese Han nationality. The Hb variant can be detected by glycated Hb electrophoresis (CapillaryS2, Hb A_1c program). However, Hb fractions analyzed by capillary electrophoresis (CE) (CapillaryS2, Hb program) and high performance liquid chromatography (HPLC), (VARIANT II™ β-Thalassemia Short Program) showed no suspicious Hb variant. Sanger sequencing revealed a novel mutation [α67(E16)Thr→Ile, HBA2: c.203C>T]. We named this novel variant Hb Sichuan after the geographic origin of the proband.

Hemoglobin Providence (β82 Lys > Asn, Asp) and lower-than-expected HbA1c in a nonadherent teenager with type 1 diabetes: a case report and literature review

Endocrinologists should have a high index of suspicion for a Hb variant when the HbA1c is not consistent with other indices of glycemic control.

Novel interactions of two α-Hb variants with SEA deletion α0-thalassemia: hematological and molecular analyses

OBJECTIVES

To report the hematological and molecular features as well as diagnostic aspects of the hitherto un-described interactions of two rare α-globin chain variants with α⁰-thalassemia commonly found among Southeast Asian populations.

METHODS

The study was done on two adult Thai patients (P1 and P2) who had hypochromic microcytic anemia. Hb analysis was carried out using high performance liquid chromatography (HPLC) and capillary electrophoresis (CE). Mutations were identified by PCR and related techniques.

RESULTS

Hb analysis of P1 using HPLC showed a normal Hb pattern, but CE demonstrated an abnormal peak at zone 7. DNA sequencing identified a CCG-CTG mutation at codon 95 of the α2 globin gene corresponding to the Hb G-Georgia [α95(G2)Pro → Leu(α2)] previously undescribed in the Thai population. In contrast, Hb analysis of P2 demonstrated an abnormal peak not fully separated from Hb A on HPLC, but not on CE. DNA analysis identified the rarely described Hb Nakhon Ratchasima [α63(E12)Ala → Val(α2)] mutation. Routine DNA analysis detected the SEA deletion α⁰-thalassemia in trans to the Hb variants in both cases. Hematological parameters were compared with those of patients with compound heterozygote for other α-globin variants and α⁰-thalassemia previously documented.

CONCLUSIONS

Identification of the patients confirmed that interaction of these rare Hb variants with α⁰-thalassemia does not lead to the Hb H disease. Differentiation of these two Hb variants from other clinically relevant hemoglobinopathies in a routine setting is, however, necessary. This can be accomplished using a combined Hb-HPLC and CE analysis followed by PCR-RFLP assays.

Interaction between Hb E and Hb Yala (HBB:c.129delT); a novel frameshift beta globin gene mutation, resulting in Hemoglobin E/β0 thalassemia

OBJECTIVES

There are more than 200 known mutations found in patients with β-thalassemia, a possibility to identify an unknown or novel mutation becomes less possible. Here, we report a novel mutation in a patient from Thailand who presented with chronic hemolytic anemia.

METHODS

A comprehensive hematology and DNA analysis was applied in the index patient and her mother.

RESULTS

Hematological and hemoglobin analyses were consistent with the clinical diagnosis of Hb E/β⁰-thalassemia. However, we could find only Hb E heterozygous mutation using our common polymerase chain reaction-based mutation detection of the β-globin genes. Furthermore, the molecular analysis demonstrated a novel T-deletion at codon 42 of the second exon of the β-globin gene which we named 'Hb Yala' according to the origin of this index family.

DISCUSSION

This mutation was assumed to generate a truncated β-globin chain terminating at codon 60 with possible unstable variant leading to a 'null' or β⁰-thalassemia. However, the clinical phenotype was surprisingly mild and no other ameliorating genetic factors, including co-inheritance of α-thalassemia and high propensity of Hb F by Xmn I polymorphism, were found.

CONCLUSION

This report has provided evidence that genotype-phenotype correlation in thalassemia syndromes is highly complex and a correct clinical severity classification of thalassemia should be mainly based on clinical evaluation.

Scanning for α-Hemoglobin Variants by High-Resolution Melting Analysis

BACKGROUND

Definitive detection of hemoglobin (Hb) variants requires DNA sequencing. High-resolution melting (HRM) analysis of polymerase chain reaction (PCR) amplicons was applied to detect and discriminate among uncommon α-Hb variants found in Thailand.

METHODS

Uncommon suspected α-Hb variants observed in Hb typing were identified by sequencing of DNA from whole blood samples. Three pairs of PCR primers covering the mutation regions in the three α-globin exons then were used for PCR coupled with difference in HRM analysis to subtract out the concomitant melting profile of the normal allele in the heterozygous state.

RESULTS

DNA sequencing identified six heterozygous α-Hb variants, namely, Hb G-Waimanalo (HBA2: exon 2, codon 64 G>A), Hb J-Buda (HBA1: exon 2, codon 61 G>T), Hb Kurosaki (HBA2: exon 1; codon 7 A>G), Hb O-Indonesia (HBA1: exon 3 codon 116 G>A), Hb Q-India (HBA1:exon 2, codon 64 G>C), and Hb Q-Thailand (HBA1: exon 2 codon 74 G>C). Difference HRM analysis showed one temperature melting profile using exon 1 primer pair, four different profiles with exon 2 primer pair, and one profile with exon 3 primer pair.

CONCLUSIONS

PCR-HRM analysis was effective in detecting and discriminating among single point mutations causing six uncommon α-Hb variants in heterozygous individuals. The method can be applied for routine screening due to its simplicity and relatively low cost.

Identification of the First Japanese Family Harboring a Novel Hemoglobin Variant "Perpignan", Which Caused Low HbA1c Measurement During Diabetic Follow-Up

Hemoglobin A1c (HbA1c) is an important parameter for evaluating long-term (6-8 weeks) control of blood glucose levels in patients with diabetes mellitus. We report a Japanese diabetic case who harbored abnormal Hb and demonstrated falsely low HbA1c levels in the regular ion exchange HPLC-based assay. His abnormal β-globin chain had an amino acid replacement that corresponded to glycine to serine substitution at amino acid position 136 of the β-globin chain (Hb Perpignan). Accordingly, a heterozygotic point mutation replacing guanine by adenine at nucleotide position 406 (β136G > S) was identified in the β-globin gene of the proband and his son. These results indicate that the patient had Hb Perpignan, and this abnormal Hb interfered with the HPLC-based HbA1c assay commonly used in the clinic. The cases presented are the first report of patients in the Japanese population harboring Hb Perpignan (β136G > S).