Hb Limassol [beta8(A5)Lys-->Asn]: a new hemoglobin variant

A Novel Pathogenic β-Thalassemia Mutation Identified at Codon 8 (HBB: c.27delG) in a Bangladeshi Family Acquired De Novo

In Bangladesh, the practice of β-thalassemia (β-thal) carrier screening and prenatal diagnosis (PND) by β-globin gene sequencing has been initiated to prevent the birth of affected children. The study aimed to describe a novel de novo mutation of the β-globin gene and its clinical implication. Out of 100 Bangladeshi β-thal carrier families, one patient with hematological and clinical features associated with β-thal and her parents were included. Molecular characterizations of β-globin gene mutations were performed by direct sequencing. A novel nucleotide deletion mutation at codon 8 in the first exon of the β-globin gene (HBB: c.27delG) was found in a 1-year-old child of the studied family in a heterozygous state along with common Hb E (HBB: c.79G>A). The mutation caused a frameshift to a new stop codon at codon 18 resulting in a β⁰-thal phenotype. The proband exhibited a β-thal intermedia (β-TI)-like genotype, however, showed β-thal major (β-TM)-like complications and was transfusion-dependent. Her mother had a profile consistent with the Hb E trait, while the father had normal hematological indices. Mutation analyses revealed the mother to be heterozygous for Hb E, while the father had a normal genotype. The novel mutation was assumed to be inherited de novo by the paternity test. The study documented a novel pathogenic mutation in the β-globin gene in a Bangladeshi family by β-globin gene sequencing.

First Report of Hb Limassol [β8(A5)Lys→Asn; HBB: c.27G>C] from Odisha, India

In this short report, we describe the clinical presentation of a rare hemoglobin (Hb) variant, Hb Limassol [β8(A5)Lys→Asn; HBB: c.27G>C] with a faster electrophoretic mobility than Hb A and that elutes in the P3 window on cation exchange high performance liquid chromatography (HPLC). This sequence variation at codon 8 (AAG>AAC) of the HBB gene was found in the four heterozygous cases, all of whom were clinically asymptomatic.

Pathology consultation on HbA(1c) methods and interferences

OBJECTIVES

To review the various hemoglobin (Hb) A1c methods, with a focus on interferences resulting from Hb variants.

METHODS

HbA1c is a marker used for the diagnosis and management of diabetes. Each available HbA1c method has advantages and challenges, such as its susceptibility to interferences.

RESULTS

The presence of Hb variants and/or abnormalities in RBC turnover cannot only interfere analytically with HbA1c measurements but also may affect the clinical interpretation of HbA1c values.

CONCLUSIONS

Familiarity with the advantages and challenges of the various methods used for HbA1c testing is essential when establishing therapeutic management and goals based on HbA1c results, especially in populations with a high prevalence of Hb variants.

Self-catalytic DNA depurination underlies human β-globin gene mutations at codon 6 that cause anemias and thalassemias

The human β-globin gene contains an 18-nucleotide coding strand sequence centered at codon 6 and capable of forming a stem-loop structure that can self-catalyze depurination of the 5'G residue of that codon. The resultant apurinic lesion is subject to error-prone repair, consistent with the occurrence about this codon of mutations responsible for 6 anemias and β-thalassemias and additional substitutions without clinical consequences. The 4-residue loop of this stem-loop-forming sequence shows the highest incidence of mutation across the gene. The loop and first stem base pair-forming residues appeared early in the mammalian clade. The other stem-forming segments evolved more recently among primates, thereby conferring self-depurination capacity at codon 6. These observations indicate a conserved molecular mechanism leading to β-globin variants underlying phenotypic diversity and disease.

Hemoglobin variants in Cyprus

Cyprus, located at the eastern end of the Mediterranean region, has been a place of eastern and western civilizations, and the presence of various hemoglobin (Hb) variants can be considered a testimony to past colonizations of the island. In this study, we report the structural Hb variants identified in the Cypriot population (Greek Cypriots, Maronites, Armenians, and Latinos) during the thalassemia screening of 248,000 subjects carried out at the Thalassaemia Centre, Nicosia, Cyprus, over a period of 26 years. A sample population of 65,668 people was used to determine the frequency and localization of several of the variants identified in Cyprus. The localization of some of the variants in regions where the presence of foreign people was most prevalent provides important clues to the origin of the variants. Twelve structural variants have been identified by DNA sequencing, nine concerning the beta-globin gene and three concerning the alpha-globin gene. The most common beta-globin variants identified were Hb S (0.2%), Hb D-Punjab (0.02%), and Hb Lepore-Washington-Boston (Hb Lepore-WB) (0.03%); the most common alpha-globin variant was Hb Setif (0.1%). The presence of some of these variants is likely to be directly linked to the history of Cyprus, as archeological monuments have been found throughout the island which signify the presence for many years of the Greeks, Syrians, Persians, Arabs, Byzantines, Franks, Venetians, and Turks.