Evaluation of HPFH and δβ-thalassemia mutations in a Brazilian group with high Hb F levels

Identification of a rare [Gγ(Aγδβ)0] -thalassemia using tandem mass spectrometry

Thalassemias are a group of inherited monogenic disorders characterized by defects in the synthesis of one or more of the globin chain subunits of the hemoglobin tetramer. Delta-beta (δβ-) thalassemia has large deletions in the β globin gene cluster involving δ- and β-globin genes, leading to absent or reduced synthesis of both δ- and β-globin chains. Here, we used direct globin-chain analysis using tandem mass spectrometry for the diagnosis of δβ-thalassemia. Two cases from unrelated families were recruited for the study based on clinical and hematological evaluation. Peptides obtained after trypsin digestion of proteins extracted from red blood cell pellets from two affected individuals and their parents were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Mass spectrometric analysis revealed a severe reduction in δ, β, and Aγ globin proteins with increased Gγ globin protein in the affected individuals. The diagnosis of Gγ(Aγδβ)0 -thalassemia in the homozygous state in the affected individuals and in the heterozygous state in the parents was made from our results. The diagnosis was confirmed at the genetic level using multiplex ligation-dependent probe amplification (MLPA). Our findings demonstrate the utility of direct globin protein quantitation using LC-MS/MS to quantify individual globin proteins reflecting changes in globin production. This approach can be utilized for accurate and timely diagnosis of hemoglobinopathies, including rare variants, where existing diagnostic methods provide inconclusive results.

Molecular characterization of a novel homozygous deletion in β-globin cluster causing (δβ)0-Thalassemia among Tunisian family

BACKGROUND

Deletions in the β-globin cluster are uncommon and cause thalassemia (thal) with hereditary persistence of fetal hemoglobin. They constitute a heterogenous group of disorders characterized by absent or reduced synthesis of adult hemoglobin (Hb A) and increased synthesis of fetal hemoglobin (Hb F). Although the clinical severity of these disorders are asymptomatic owing to the increased Hb F levels, the molecular basis is very heterogenous due to the large deletions in the β-globin cluster spanning both HBD and HBB genes. Here, we describe a Tunisian family carrying a novel deletion mutation causing (δβ)°-thalassemia.

METHODS

The amounts of hemoglobin fractions were measured by capillary electrophoresis of hemoglobin. Amplification and sequencing of different regions on the β-gene cluster were performed by Sanger method.

RESULTS

Family study and genetic analysis revealed a large deletion mutation in the β-globin cluster of 14.5 kb (NG_000,007.3:g. 58,253 to g.72837del14584) at the homozygous state in the patient and at heterozygous state at the other members of the family. This deletion removes the HBD and HBB genes.

CONCLUSIONS

In our knowledge, this new large deletion is described for the first time in the Tunisian population and in the world, designed Tunisian(δβ)⁰ in Ithanet database (IthaID: 3971). Therefore, it is important to identify the deletion leading to δβ-thalassemia carriers at the molecular level, to highlight the importance of recognizing the clinical features and implementing appropriate testing to clarify the diagnosis and manage the condition.

Three novel HBB mutations, c.-140C>G (-90 C>G), c.237_256delGGACAACCTCAAGGGCACCT (FS Cd 78/85 -20 bp), and c.315+2T>G (IVS2:2 T>G). Update of the mutational spectrum of β-Thalassemia in Mexican mestizo patients

INTRODUCTION

Beta-thalassemia (β-thal) is frequent in Mexican patients with microcytosis and hypochromia. We report three novel mutations and analyze the actual mutational spectrum in Mexican population.

METHODS

One hundred and forty-nine β-thal Mexican mestizo patients were studied (154 alleles). ARMS-PCR was performed to identify Cd39C>T, IVS1:1G>A, IVS1:110G>A, -28A>C, initiation codonA>G and IVS1:5G>A mutations, and gap-PCR for δβ-thal Spanish type. DNA sequencing of HBB gene was carried out in negative samples for the initial screening.

RESULTS

Fifteen different HBB gene mutations were observed in 148 alleles; three of them are novel: -90C>G, 20 bp deletion (at codons 78/85), and IVS2:2T>G; the mutation IVS1:6T>C that was observed for first time in our population; and eleven previously described mutations. Six alleles showed normal HBB sequence. To date, a total of 21 different mutations have been observed in Mexican patients; the four most frequent mutations are of Mediterranean origin: Cd39C>T (37.2%), IVS1:1G>A (17.3%), IVS1:110G>A (13.9%), and δβ-thal Spanish type (9.0%), which represent 77.4% of the total studied alleles.

CONCLUSION

Considering the novel mutations -90C>G, -20 bp Cd78/85, IVS2:2T>G and the first observation of IVS1:6T>C, the molecular spectrum of β-thal in Mexicans comprises 21 different mutations, confirming the high allelic heterogeneity in Mexicans.

Incidental Identification of Possible Delta-Beta Thalassemia Trait in a Family: A Rare Cause of Elevated Hb F

Delta-Beta thalassaemia is an unusual variant of thalassaemia with elevated level of foetal haemoglobin (HbF). The clinical presentation of delta-beta thalassaemia is mild in both heterozygote and homozygote cases. We hereby describe a rare cause of elevated Hb F in a father and his two daughters. A 52-year-old diabetic male patient, on evaluation of chromatogram of cation exchange HPLC for HbA1c, we incidentally identified elevated Hb F of approximately 20%. Haematological investigation of the patient revealed decreased haemoglobin, normal RBC, leucocyte and platelet count, decreased MCV and MCH. Red cell morphology showed predominantly normocytic normochromic cells with mild anisopoikilocytosis, few microcytes and hypochromic cells seen. His liver function test was normal. Haemoglobin variant analysis revealed decreased Hb A (79.4%), normal Hb A2 (2%) and increased Hb F (19.75%). A possible diagnosis of heterozygous δ β-thalassaemia was considered. Since most laboratories perform HbA1c by cation exchange HPLC method, a careful evaluation of the chromatogram yields useful information. In our case, the elevated Hb F in a father and further careful evaluation of clinical and haematological parameters in the family members made us to possibly think of rare disorders like heterozygous Delta-Beta thalassaemia in the family and provide valuable genetic counseling.

Haematological characterisation and molecular basis of asian Indian inversion deletions delta Beta thalassemia: a case report

The hereditary persistence of fetal hemoglobin (HPFH) and delta beta thalassemia are heterogeneous disorders characterised by increased levels of fetal hemoglobin and high level of this Hb continues in adulthood. The distinction between these two conditions is not always possible with routine hematologic analysis and molecular characterisation of the defect is required. We encountered such a rare case of δ β thalassemia in a 10-year-old male child who presented with features of thalassemia intermedia. Hemoglobin analysis showed 100% HbF while molecular analysis revealed Asian Indian inversion-deletion GγAγ(δ β) zero thalassemia.