Hb A2-Calderdale [δ2(NA2)His→Asn; HBD: c.7C>A] and Misdiagnosis of Type 2 Diabetes Mellitus Due to Interference with Hb A1c When Using Cation Exchange High Performance Liquid Chromatography: A Case Report.

The Hb A2-Calderdale variant [δ2(NA2)His→Asn, HBD: c.7C>A] was described as a novel variant in 2014. However, a high performance liquid chromatography (HPLC) peak was never identified indicating that this fraction could be 'hiding' somewhere else in the chromatogram. In this case report, we present evidence that the physiochemical properties of Hb A2-Calderdale resemble those of Hb A1c, resulting in a coelution in variant mode on the Tosoh G8 but not the Tosoh G11. This coelution results in an overestimation of Hb A1c and can potentially cause misdiagnosis of type 2 diabetes mellitus (T2DM).

Detection of a Hb A2 -Melbourne (HBD: c.130G>A) combined with ß-thalassemia in a Chinese individual.

BACKGROUND: Thalassemia is common in Southeast Asian countries, including China. Hb A2 -Melbourne is a rare hemoglobin variant and has never been reported in China. Here, we report a Hb A2 -Melbourne combined with ß-thalassemia in Chinese individuals which is the second case described in the published reports. METHODS: Complete blood counts (CBC) of a 28-year-old female showed signs of thalassemia during a routine screening. Hemoglobin analysis was subsequently performed using capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). Four common deletional α-thalassemia detection was carried out using a gap-polymerase chain reaction (PCR). PCR and reverse dot-blot were used to detect three non-deletional α-thalassemia and 17 types of point mutations in ß-thalassemia. Finally, it was identified by Sanger sequencing. Her husband also had CBC, hemoglobin analysis, and genetic diagnosis. RESULTS: CBC of the couple showed Hb 103 and 139 g/L, mean corpuscular volume 58 and 63.1 fL, mean corpuscular hemoglobin 19.7 and 20.4 pg, respectively. Hemoglobin analysis revealed Hb X 2.4%, Hb A2 2.8% by CE and Hb X 2.9%, Hb A2 2.4% by HPLC in the female. The results of her husband were Hb A93.5%, Hb A2 5.7%, Hb F 0.8% by CE. Genetic analysis of both spouses detected the same CD 41/42 mutations in ß-globin gene. Sanger sequencing of female identified a mutation of the δ-globin gene (HBD:c.130G>A), corresponding to Hb A2 -Melbourne. CONCLUSION: Hb A2 -Melbourne can lead to misdiagnosis of ß-thalassemia. δ-globin gene mutation must be carefully examined in routine thalassemia screening.

Coinheritance of Hb A2-Melbourne (HBD: c.130G>A) and Hb E (HBB: c.79G>A) in Laos and Simultaneous High Resolution Melt Detection of Hb A2-Melbourne and Hb A2-Lampang (HBD: c.142G>A) in a Single Tube.

We report the molecular and hematological identifications of a Hb A2 variant [coinheritance of Hb A2-Melbourne (HBD: c.130G>A) and Hb E (HBB: c.79G>A)] found for the first time in the Lao People's Democratic Republic (PDR). The subject was a 29-year-old pregnant Laotian woman who was a foreign worker in Thailand and was diagnosed with thalassemia and hemoglobinopathies. Capillary electrophoresis (CE) demonstrated 1.6% of Hb A2, with a minor unknown peak at the initial Z1 zone (1.7%). Identification of abnormal hemoglobin (Hb) using direct DNA sequencing showed a genetic defect causing a δ-globin gene missense mutation at codon 43 (GAG>AAG) causing a glutamic acid to lysine substitution corresponding to Hb A2-Melbourne. The origin of Hb A2-Melbourne in Lao PDR may be similar to a case found in Thailand with the [+ - - - - + +] haplotype. We developed a method that could clearly detect Hb A2-Melbourne and Hb A2-Lampang (HBD: c.142G>A) mutations in a single tube using high resolution melt (HRM) analysis. The HRM analysis is a more effective method for rapid detection than conventional polymerase chain reaction (PCR), as there is no need for a post-PCR step, and no exposure to ethidium bromide. This new method would be a useful addition for the first investigation of a suspected Hb A2 variant in the routine molecular setting.

Molecular and Hematological Characterization of Two Novel δ-Globin Gene Mutations Found in Chinese Individuals.

We identified two novel δ-globin gene mutations in two families during routine thalassemia screening. One missense mutation at codon 73 on the δ-globin gene [δ73(E17)Asp→Val, HBD: c.221A>T] which results in a Hb A2 variant homologous to the ß-globin gene variant called Hb Mobile [ß73(E17)Asp→Val, HBB: c.221A>T] and we have named this variant Hb A2-Henan. The other is a nonsense mutation [δ7(A4)Glu→Stop, HBD: c.22G>T] which gives rise to a stop codon (TAG) at codon 7, resulting in δ0-thalassemia (δ0-thal). The Hb A2 in one individual with homozygous HBD: c.22G>T was absent.

Hematological and Molecular Characterization of a Novel Hb A2 Variant with Homozygous α-Thalassemia-2 in a Southern Thai Individual.

We report here the hematological and molecular features of a novel δ-globin chain variant found in a Southern Thai woman. Her complete blood count was as follows: red blood cell (RBC) count 5.90 × 1012/L, hemoglobin concentration (Hb) 12.6 g/dL, packed cell volume (PCV) 0.41 L/L, mean corpuscular volume (MCV) 69.5 fL, mean corpuscular Hb (MCH) 21.4 pg, mean corpuscular Hb concentration (MCHC) 30.7 g/dL and RBC distribution width (RDW) 13.1%. The blood smear demonstrated microcytic hypochromic RBCs suggestive of thalassemia trait. Hemoglobin analysis identified Hb A2 + Hb A2-Kiriwong (2.4%) and Hb F (0.1%) on high performance liquid chromatography (HPLC). To characterize the α-thalassemia (α-thal) genotype, common α-thal-1 and α-thal-2 alleles were characterized by multiplex gap-polymerase chain reaction (gap-PCR). The results revealed homozygous α-thal-2 (-α3.7/-α3.7) in this case. DNA sequencing showed the presence of a novel δ-globin gene mutation [δ77(EF1)His→Arg; HBD: c.233A>G] that we named Hb A2-Kiriwong for the village from where the proband lived. In summary, the presence of microcytic hypochromic RBCs in this case was likely the result of the homozygous -α3.7 (rightward) deletion and was not affected by this Hb A2 variant.

A study of δ-globin gene mutations in the UK population: identification of three novel variants and development of a novel DNA test for Hb A'2.

We report here the spectrum of δ-globin gene mutations found in the UK population. Nine different δ chain variants and two δ-thalassemia (δ-thal) mutations were characterized in a study of 127 alleles in patients with either a low Hb A2 value or a split Hb A2 peak on high performance liquid chromatography (HPLC). The most common δ chain variant was Hb [Formula: see text] (or Hb B2) [δ16(A13)Gly → Arg; HBD: c.49G > C] (77.0%), followed by Hb A2-Yialousa [δ27(B9)Ala → Ser; HBD: c.82G > T] (12.0%), Hb A2-Babinga [δ136(H14)Gly → Asp; HBD: c.410G > A] (3.0%), Hb A2-Troodos [δ116(G18)Arg → Cys; HBD: c.349C > T] (1.0%), Hb A2-Coburg [δ116(G18)Arg → His; HBD: c.350G > A] (2.0%) and Hb A2-Indonesia [δ69(E13)Gly → Arg; HBD: c.208G > C] (1.0%). Three novel variants were identified: Hb A2-Calderdale [codon 2 (CAT > AAT), His → Asn; HBD: c.7C > A], Hb A2-Walsgrave [codon 52 (GAT > CAT), Asp → His; HBD: c.157G > C] and Hb A2-St. George's [codon 81 (CTC > TTC), Leu → Phe; HBD: c.244C > T]. In addition, two known δ-thal mutations were observed: -68 (C > T); HBD: c.-118C > T and codon 4 (ACT > ATT); HBD: c.14C > T. Amplification refractory mutation system (ARMS) primers were developed to provide a simple molecular diagnostic test for the most common variant, Hb [Formula: see text]. Three of the variants had a characteristic HPLC retention time that can be used for a presumptive diagnosis.

Known and new δ-globin gene mutations and other factors influencing Hb A2 measurement in the Omani population.

Although δ-thalassemia (δ-thal) is not categorized as a severe disease, it is essential to know the molecular spectrum of the δ gene mutations frequently occurring in specific areas, particularly if these areas are characterized by a high rate of ß-thalassemia (ß-thal) such as Oman. This is because coinherited δ-globin gene defects can interfere with the basic diagnosis of a ß-thal carrier when this is based upon the measurement of the Hb A2 only. Because of that, we have investigated 33 patients with low Hb A2 levels, collected from different hospitals in Oman. Some cases had a second Hb A2 fraction, while others had only significantly lower Hb A2 levels. Among these patients, 20 did carry a δ-globin gene mutation, the rest were carriers of α thalassemia (α-thal) defects or could be iron depleted or both. In total, eight different known mutations and two novel δ variants were found. The characterization of the δ-globin gene mutation spectrum will improve carrier diagnostics and genetic counseling in the Omani population screened for ß-thal.

Hemoglobin A2 and Heterogeneous Diagnostic Relevance Observed in Eight New Variants of the Delta Globin Gene.

BACKGROUND: Hemoglobin A (Hb A) (α2ß2) in the normal adult subject constitutes 96-98% of hemoglobin, and Hb F is normally less than 1%, while for hemoglobin A2 (Hb A2) (α2δ2), the normal reference values are between 2.0 and 3.3%. It is important to evaluate the presence of possible delta gene mutations in a population at high risk for globin gene defects in order to correctly diagnose the ß-thalassemia carrier. METHODS: The most used methods for the quantification of Hb A2 are based on automated high performance liquid chromatography (HPLC) or capillary electrophoresis (CE). In particular Hb analyses were performed by HPLC on three dedicated devices. DNA analyses were performed according to local standard protocols. RESULTS: Here, we described eight new δ-globin gene variants discovered and characterized in some laboratories in Northern Italy in recent years. These new variants were added to the many already known Hb A2 variants that were found with an estimated frequency of about 1-2% during the screening tests in our laboratories. CONCLUSIONS: The knowledge recognition of the delta variant on Hb analysis and accurate molecular characterization is crucial to provide an accurate definitive thalassemia diagnosis, particularly in young subjects who would like to ask for a prenatal diagnosis or preimplantation genetic diagnosis.

Delta-Globin Gene Expression Is Enhanced in vivo by Interferon Type I.

Beta hemoglobinopathies are widely spread monogenic lethal diseases. Delta-globin gene activation has been proposed as a possible approach for curing these pathologies. The therapeutic potential of delta-globin, the non-alpha component of Hemoglobin A2 (α2δ2; HbA2), has been demonstrated in a mouse model of beta thalassemia, while its anti-sickling effect, comparable to that of gamma globin, was established some time ago. Here we show that the delta-globin mRNA level is considerably increased in a Deoxyribonuclease II-alpha knockout mouse model in which type 1 interferon (interferon beta, IFNb) is activated. IFNb activation in the fetal liver improves the delta-globin mRNA level, while the beta-globin mRNA level is significantly reduced. In addition, we show that HbA2 is significantly increased in patients with multiple sclerosis under type 1 interferon treatment. Our results represent a proof of principle that delta-globin expression can be enhanced through the use of molecules. This observation is potentially interesting in view of a pharmacological approach able to increase the HbA2 level.

First report of the spectrum of δ-globin gene mutations in Omani subjects - identification of novel mutations.

INTRODUCTION: Both coinheritance of thalassemic δ-globin mutation and coexistence of iron deficiency anemia (IDA) tend to decrease HbA2 (α2 δ2 ) level and thereby poses a diagnostic conundrum in ß-thalassemia trait. METHODS: We retrospectively studied 78 Omani subjects, presenting with low HbA2 level by high-performance liquid chromatography (HPLC), and their DNA was sequenced for the presence of mutations in the δ-globin gene (HBD). In these subjects, their serum ferritin levels allowed evaluation of the degree of iron deficiency. RESULTS: Overall, six different δ-globin gene mutations were observed in 40 study subjects (51.3%) and IDA in 33 subjects, with the remaining five subjects showing normal HBD sequence and serum ferritin level. Among the subjects with δ-globin gene mutations, seven had an associated IDA confirmed by significantly low serum ferritin levels. Heterozygosity for the delta (+) cd27G-->T mutation (HbA2 -Yialousa; HBD: c.82G>T) was the most common abnormality observed (n = 26, 66.6%) followed by heterozygosity for HBD c.-118C->T (d -68 C->T) (n = 6, 15.4%), for cd16G-->C (n = 4, 10.3%), for cd98G-->A (n = 2, 5.1%), for cd142G-->C (n = 1, 2.6%), and for cd147G-->T (n = 1, 2.6%). CONCLUSIONS: These delta mutations exhibit low HbA2 either due to a shift in the HPLC position or due to their bona fide thalassemic feature. Two mutations, namely cd142 G-->C (GCC to CCC, Ala to Pro) and stop codon cd147 G-->T (stop to Leu with elongation of 15 amino acids), herein first reported are novel. Coexistence of IDA could lead to erroneous diagnostic interpretation unless it is specifically looked for.