Newborn Screening for ß-Thalassemia Identifies a Complex Genotype Involving a Novel ß-Globin Gene Mutation (HBB:c.336dup).

Newborn screening identified a Chinese-Canadian infant who was positive for possible ß-thalassemia (ß-thal). Detailed family studies demonstrated that the proband was a compound heterozygote for the Chinese Gγ(Aγδß)0-thal deletion and a novel frameshift mutation within exon 3 (HBB:c.336dup), and heterozygous for the Southeast Asian α-thal deletion (--SEA/αα). This case illustrates the importance of follow-up molecular testing of positive newborn screening results to confirm the diagnosis and define risks for future pregnancies.

ß0-Thalassemia Caused by a Novel Nonsense Mutation [HBB:c.199A > T].

We report two hemoglobinopathy cases involving a novel ß-thalassemia (ß-thal) nonsense mutation, HBB:c.199A > T. One patient had Hb S/ß-thal, and a second unrelated patient had Hb D-Punjab/ß-thal. The HBB:c.199A > T mutation introduces a premature termination codon at amino acid codon 66 (AAA→TAA) in exon 2, resulting in typical high Hb A2 ß0-thal.

Splice Acceptor Mutation [HBB:c.93-2A > T] in a Patient with Hb S/ß0-Thalassemia.

We report a case of Hb S/ß0-thalassemia (Hb S/ß0-thal) in a patient who is a compound heterozygote for the Hb Sickle mutation (HBB:c.20A > T) and a mutation of the canonical splice acceptor sequence of IVS1 (AG > TG, HBB:c.93-2A > T). This is the fifth mutation involving the AG splice acceptor site of IVS1, all of which prevent normal splicing and cause ß0-thal.

Characterization of Two Novel Deletions Involving the 5' Region of the ß-Globin Gene.

We report two novel ß-thalassemia (ß-thal) deletions involving the 5' region of the ß-globin gene (HBB). The first deletion spans 538 bp and removes the ß-globin promoter, 5' untranslated region (5'UTR) and most of exon 1. This deletion was identified in a 3-year-old Vietnamese boy with non transfusion dependent Hb E (HBB: c.79G>A)/ß0-thal. The second deletion spans 1517 bp and removes the ß-globin gene promoter, 5'UTR, and exons 1 and 2. This deletion was identified in two unrelated adults of European descent who had ß-thal trait with unusually high Hb A2 levels. Deletions such as these are generally associated with higher levels of Hb A2 and Hb F than typical ß-thal alleles, which may ameliorate the severity of the disease.

α0-Thalassemia Due to a 90.7 kb Deletion (- -NFLD).

We report an α0-thalassemia (α0-thal) trait in Newfoundlanders caused by a novel 90.7 kb deletion. The deletion, designated the Newfoundland deletion (- -NFLD), removes both the HBA2 and HBA1 genes, while leaving the HBZ gene intact. The 5' deletion endpoint is within the HBAP1 pseudogene, approximately 3.7 kb upstream of the HBA2 gene. The 3' deletion endpoint is approximately 82.5 kb downstream of the HBA1 gene, within the second intervening sequence (IVS-II) of the FAM234A gene. This is the second α0-thal deletion reported in Newfoundland families of northern European descent.

Novel Mutation of the Translation Initiation Codon of the α1-Globin Gene (ATG>AAG or HBA1:c.2T>A).

We report two Italian-Canadian families with α+-thalassemia (α+-thal) trait caused by a novel mutation of the translation initiation codon of the α1-globin gene (ATG>AAG or HBA1:c.2T>A). This is the tenth reported α-thal mutation involving the translation initiation codon or the conserved Kozak consensus sequences of the HBA2 or HBA1 genes.

Sudanese (뫧)0-Thalassemia: Identification and Characterization of a Novel 9.6 kb Deletion.

We report a case of δß-thalassemia (δß-thal) trait in an adult male originally from Sudan. Multiplex ligation-dependent probe amplification (MLPA) was used to localize the approximate boundaries of the deletion, followed by polymerase chain reaction (PCR) amplification and sequence analysis of the junction fragment to determine the precise deletion endpoints. The deletion spans 9594 bp, with the 5' deletion endpoint located 1560 bp upstream of the δ-globin gene and the 3' endpoint within the second intervening sequence (IVS-II) of the ß-globin gene.

α(+)-Thalassemia Due to a Frameshift Mutation of the α2-Globin Gene [codons 55/56 (+T) or HBA2: c.168dup].

We report a case of α(+)-thalassemia (α(+)-thal) trait in a Chinese-Canadian family caused by a novel frameshift mutation of the α2-globin gene, specifically the duplication of a single nucleotide at amino acid codon 56 [HBA2: c.168dup]. The mutation results in substitution of a termination codon (TAA) for lysine (AAG) at amino acid position 56.

Non-thalassemic phenotype associated with the -83 (G > A) mutation of the ß-globin gene promoter (HBB: c.-133G > A).

The -83 (G > A) mutation of the ß-globin gene promoter (HBB: c.-133G > A) was first reported in an adult male patient with mild thalassemic indices, suggesting that this may be a mild ß(+)-thalassemia (ß(+)-thal) allele. In this report, we present data from several patients who are simple heterozygotes for the -83 mutation, or compound heterozygotes for -83 and Hb S (HBB: c.20A > T) or ß-thal. These cases illustrate that the -83 sequence variant is not associated with a thalassemic phenotype. This has important implications for carrier screening and genetic counseling, particularly since the -83 mutation is relatively common in African and Hispanic populations.

Mild ß(+)-thalassemia associated with two linked sequence variants: IVS-II-839 (T>C) and IVS-II-844 (C>A).

We report four unrelated families with a mild ß(+)-thalassemia (ß(+)-thal) allele consisting of two sequence variants at the 3' end of IVS-II: IVS-II-839 (T>C) (HBB: c.316-12T>C) and IVS-II-844 (C>A) (HBB: c.316-7C>A). These sequence variants alter the conserved polypyrimidine tract of the consensus splice acceptor sequence (Y11NYAG/G), which could reduce splicing efficiency. This may represent a common, yet under-diagnosed ß(+)-thal allele in African populations.

Normal Hb A2 ß-thalassemia trait: frameshift mutation (HBB: c.187_251dup) in cis with the Hb A2' δ-globin gene missense mutation (HBD: c.49G>C).

We report the case of a father and daughter who are heterozygous for a duplication of 65 bp within exon 2 of the ß-globin gene, resulting in an altered and truncated ß-globin chain that is predicted to be non functional. The ß-globin gene mutation is in cis with the common Hb A2 ' missense mutation of the δ-globin gene (HBD: c.49G>C), resulting in ß-thalassemia (ß-thal) trait with normal levels of Hb A2. This is the second report of this ß(0)-thal mutation, and both families were associated with the Hb A2 ' variant and normal levels of Hb A2. Laboratories should be aware of the rare occurrence of ß-thal trait with normal levels of Hb A2.

α(+)-Thalassemia trait caused by a frameshift mutation in exon 2 of the α2-globin gene [HBA2 c.244delT].

We report a case of α(+)-thalassemia (α(+)-thal) trait caused by a novel frameshift mutation in exon 2 of the α2-globin gene, specifically a deletion of a single nucleotide at amino acid codon 81 [HBA2 c.244delT]. The mutation results in a premature termination of translation at codon 83.

Characterization of three novel delta chain hemoglobin variants and two delta-thalassemia alleles.

We report the characterization of five novel delta-globin gene mutations detected during routine screening for thalassemia. Three missense mutations were identified, resulting in the following delta chain hemoglobin (Hb) variants: Hb A(2)-Acacias [delta4 (ACT>AGT), Thr-->Ser, HBD c.14C>G], Hb A(2)-Toronto [delta74 (GGC>GAC), Gly-->Asp, HBD c.224G>A], and Hb A(2)-Calgary [delta99 (GAT>GGT), Asp-->Gly, HBD c.299A>G]. Two other mutations most likely result in delta(0)-thalassemia (delta(0)-thal). One mutation altered the translation initiation codon from ATG to ATA (HBD c.3G>A), and another changed the canonical splice donor sequence of IVS-II from GT to AT (HBD C.315+1G>A).

Three new beta-thalassemia mutations with varying degrees of severity.

We report the identification of three, new beta-thalassemia (beta-thal) mutations with varying degrees of severity. The most severe mutation, a frameshift mutation in exon 3 of the beta-globin gene [codon 120 (-A)], was associated with a dominant beta-thal phenotype. A second frameshift mutation, codon 50 (-T), resulted in a phenotype of typical high Hb A(2) beta-thal trait. The mildest mutation was IVS-II-2 (T > C), which changes the splice donor sequence of IVS-II from GT to GC. This transition mutation resulted in a slight reduction in beta-globin gene expression and could be considered a mild beta(+)-thal allele.

Hb North York [beta 117(G19)His-->Asp]: a new beta chain hemoglobin variant.

Routine hemoglobin (Hb) analysis identified a new beta chain Hb variant in an Iranian woman, who otherwise had normal hematological indices. Sequence analysis demonstrated that the Hb variant was due to a missense mutation at amino acid codon 117 (CAC>GAC, His-->Asp) of the beta-globin gene.

Alpha+-thalassemia trait caused by a nonsense mutation in the alpha2-globin gene: codon 54 (CAG>TAG).

We report a new alpha-thalassemia (alpha-thal) point mutation detected in a woman with alpha(+)-thal trait. Sequence analysis identified a nonsense mutation in exon 2 of the alpha2-globin gene, at amino acid codon 54 (CAG>TAG).

Three new beta-globin gene promoter mutations identified through newborn screening.

We report three new beta-globin gene promoter mutations identified in newborns with hemoglobin (Hb) profiles consistent with Hb S/beta(+)-thalassemia (thal) (Hbs FSA). All three mutations are in close proximity to the conserved ATAA sequence located at positions -31 to -28 relative to the mRNA Cap site. Two cases involved single base substitutions at positions -25 (G-->C) and -32 (C-->T). The remaining case involved the deletion of two bases (-AA) at positions -27 and -26.

High oxygen affinity hemoglobin variant in a Canadian family: Hb Bunbury [beta94(FG1)Asp-->Asn, GAC-->AAC].

We investigated a three-generation Canadian family in which individuals displayed varying degrees of erythrocytosis due to a high oxygen affinity beta chain hemoglobin (Hb) variant [Hb Bunbury, beta94(FG1)Asp-->Asn, GAC-->AAC]. This is the fourth reported case of Hb Bunbury.