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.

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.

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.

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.

Prenatal diagnosis of hemoglobinopathies in Ontario, Canada.

In 1989, the Province of Ontario established a molecular diagnostic laboratory for carrier detection and prenatal diagnosis of hemoglobinopathies. Over the past 15 years, the laboratory has provided prenatal diagnosis for 672 pregnancies at-risk for severe hemoglobinopathies: 276 (41%) for homozygous beta-thalassemia or hemoglobin (Hb) E/beta-thalassemia, 211 (31%) for homozygous alpha 0-thalassemia (Hb Bart's hydrops fetalis), and/or Hb H disease, and 185 (28%) for various sickling disorders (Hb SS, Hb SC, Hb S/beta-thalassemia). Despite the availability of services for carrier screening, genetic counseling, and prenatal diagnosis, there has been only a modest reduction in the overall incidence of hemoglobinopathies in Ontario.

Identification of nine novel DHCR7 missense mutations in patients with Smith-Lemli-Opitz syndrome (SLOS).

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive, multiple congenital anomaly syndrome caused by deficiency of 7-dehydrocholesterol reductase (DHCR7), which catalyzes the last step of endogenous cholesterol synthesis. Surveys of SLOS patients have identified more than one hundred point mutations of the DHCR7 gene, most of which are missense mutations. Here, we report the identification of nine novel missense mutations of the DHCR7 gene.

Founder effect for the T93M DHCR7 mutation in Smith-Lemli-Opitz syndrome.

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive MCA-MR disorder caused by mutations within the 7-dehydrocholesterol reductase gene, DHCR7. The diagnosis is based on the biochemical findings of elevated plasma 7-dehydrocholesterol (7DHC) levels. It is a panethnic condition with variable mutation frequencies in different populations. Ten Cuban patients and four Canadian patients of Mediterranean ancestry with SLOS are reported herein. All these patients are at the mild end of the clinical spectrum (the highest Kelley-Hennekam severity score was 28 in one patient). All patients had genotypes which were compound heterozygous or homozygous for T93M; in all the Mediterranean patients the T93M mutation appeared to be associated with the J haplotype. Another compound heterozygote for T93M was of Ukrainian/Irish ancestry; in this patient the T93M was associated with a new haplotype designated K. The T93M mutation was initially reported as the most common in a series of patients from Italy. Our identification of a single haplotype associated with the T93M mutation in patients whose ancestors originate in the region of the Mediterranean Sea basin suggests a founder effect.

Beta-thalassemia in association with a new delta-chain hemoglobin variant [delta116(g18)Arg-->Leu]: implications for carrier screening and prenatal diagnosis.

We describe a complicated genetic counseling and prenatal diagnostic case involving an East Indian couple that had lost two consecutive pregnancies. Hemoglobinopathy screening was conducted to investigate the possibility of Hb Bart's hydrops fetalis or Hb H hydrops fetalis. The initial work-up indicated that alpha-thalassemia was not a contributing factor, with both parents being carriers of single gene deletions (-alpha(3.7)/alphaalpha). However, the Hb electrophoresis results indicated that the couple might be at risk for having children with Hb E/Hb Lepore disease. Subsequent DNA testing demonstrated that the father carried the Hb E mutation, but failed to confirm that the mother carries the Hb Lepore deletion. Sequence analysis revealed that the mother was heterozygous for a common East Indian beta(0)-thalassemia mutation, yet had a normal level of Hb A(2). The mother also carried a previously unreported missense mutation of the delta-globin gene, in cis with the beta(0)-thalassemia mutation, which gave rise to the minor Hb variant originally misidentified as Hb Lepore. This case illustrates the importance of comprehensive molecular analyses for accurate assessment of genetic risks for hemoglobinopathy syndromes.