Molecular Basis of α-Thalassemia in Algeria

An epidemiological molecular study was carried out to evaluate the spectrum and allelic frequency of α-thalassemia (α-thal) defects in Algeria. A series of 153 randomly selected blood donors was screened for 10 α-thal alleles described in the Mediterranean area. In addition, six unrelated cases with hematological and biochemical data suggestive of Hb H disease were investigated. Our data revealed an allele frequency of 4.6%. The presence of α⁰-thal determinants (?α^20.5 and – –^{MED I}) was observed both in Hb H patients and in the randomly collected samples. Overall, the ?α^3.7 deletion was the most prevalent allele (2.9%), followed by the α^{Nco I}α (HBA2:c.1A>G) allele (0.6%) and by the α^{Hph I}α (HBA2:c.95 + 2_95 + 6delTGAGG), ?α^20.5, – –^{MED I} alleles (0.3% each). The ?α^4.2 deletion was observed in only one Hb H patient. These results outline the heterogeneity of the α-thal alleles in Algeria which reflects the anthropological history of the country. Because of their frequency, α-thal alleles are probably frequent modulators of prevalent β-globin gene-related hemoglobinopathies in Algeria.     

Hematological and Molecular Findings in the First Case of Hb J-Norfolk [HBA2: c.173G>A (or HBA1] in an Indian Patient

Abstract

We here report a case of a 23-year-old female from Mumbai, Maharashtra, India who was detected to carry the α chain variant Hb J-Norfolk [HBA2: c.173G>A (or HBA1]. She had no clinical symptoms and was referred to us for routine investigations and screening. An abnormal peak was detected on both high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) with a fast-moving band on cellulose acetate electrophoresis. There is no detailed study on the HPLC and CE pattern of this hemoglobin (Hb) variant, and therefore, this study will help in detecting and avoiding missing these variants during routine investigations and population screening. This is the first report of this variant in the Indian population.     

Hb Hinwil [β38(C4)Thr→Asn,ACC>AAC] Associated with β0-Thalassemia in a Sicilian Child

Hemoglobins (Hbs) with high oxygen affinity play a well-known role among the causes of erythrocytosis. In 1996, a new Hb called Hb Hinwil or β38(C4)Thr→Asn was described. In carriers, it causes an increase in the number of red blood cells, total Hb, and hematocrit. Here we report the case of a patient, aged 10 months, whom we observed because of severe erythrocytosis. The family history of β-thalassemia (β-thal) inheritance, and the evidence in the patient of marked microcytosis, prompted us to perform molecular analysis to detect β gene mutations that revealed a codon 39 (C>T) (β⁰) mutation in the heterozygous state and the presence of the Hb Hinwil mutation on the other allele. We discuss diagnostic, clinical, prognostic, and therapeutic aspects of this rare condition, underlining the extreme difficulty in choosing therapeutic options because of a lack of similar reports in the literature.     

Neonatal Cyanosis Due to a Novel Fetal Hemoglobin: Hb F-Circleville [Gγ63(E7)His→Leu,CAT>CTT]

Neonatal cyanosis can result from a multitude of acquired and inherited causes. Cyanosis resulting from fetal M hemoglobin (Hb) variants is very rare. Only two ^Gγ variants causing methemoglobinemia and cyanosis in the newborn have been reported to date. Here we describe a novel fetal Hb variant, Hb F-Circleville [^Gγ63(E7)His→Leu], associated with methemoglobinemia and cyanosis in the newborn. The patient's sister also had neonatal cyanosis at birth.     

Double Heterozygosity for Hb Durham-N.C. (HBB: c.344T>C) [β114(G16)Leu→Pro] and the IVS-I-110 (HBB: c.93-21G>A) Causing a Severe β-Thalassemia Phenotype

Abstract

The evaluation of a 10-month-old girl of Sicilian origin with a clinical phenotype of severe thalassemia led to the identification of two β-globin gene defects, a β-thalassemia (β-thal), mutation at IVS-I-110 (HBB: c.93-21G>A) and a variant hemoglobin (Hb) mutation at codon 114 (HBB: c.344T>C) on the other allele, reported as Hb Durham-N.C. (also known as Hb Brescia) [β114(G16)Leu→Pro] in the HbVar database. A very low Hb level (Hb 3.5?g/dL), microcytosis [mean corpuscular volume (MCV) 63.2 fL] and hypocromia [mean corpuscular Hb (MCH) 19.6?pg], increased red blood cell (RBC) distribution width (RDW) (36.0%), higher reticulocytes (6.2%), anisocytosis, poikilocytosis, hypocromia, basophilic stippling and inclusion body formation, were present in the affected subject. Analysis of other family components showed the presence of HBB: c.93-21G>A defect in the mother and in her brother, while Hb Durham-N.C. was absent in all other relatives, thus, this mutation has arisen as a de novo defect. This is the first case described as a severe thalassemic phenotype in a compound heterozygote carrier of this unstable Hb and a common β-thalassemic allele. The important information gained from this case is that a rare dominant or recessive mutation may arise in every individual, even if this is a very rare event.     

Further Identification of The Hyperunstable α-Globin Chain Variant Hb Heraklion [codons 36/37 (–CCC); Pro→0 (α1)] in Greek Cases With Co-Inherited α+-Thalassemia Mutations

We report four Greek cases (from three unrelated families), who all had a similar atypical thalassemia intermedia phenotype, characterized by chronic moderate anemia, mild hemolysis and splenomegaly in the absence of abnormal hemoglobin (Hb) fractions. In all four cases (two unrelated children and two siblings), DNA analysis identified common α⁺-thalassemia (α⁺-thal) mutations in trans to the in frame 3 bp deletion (?CCC) on the α1-globin gene between codons 36 and 37, which has previously been reported as Hb Heraklion in a single Greek case. Clinical, hematological and biochemical findings in all cases, including a follow-up evaluation of the original case, are described. All the cases originated from the Greek island of Crete.     

Methemoglobin Forming Effect of Dimethyl Trisulfide in Mice

Abstract

Dimethyl trisulfide (DMTS) is a natural organic trisulfide that has been patented as a promising antidotal candidate against cyanide (CN). The primary mode of action of DMTS is as a sulfur donor that enables the conversion of CN to thiocyanate. Recently, it was discovered that DMTS is capable of oxidizing hemoglobin (Hb) to methemoglobin (MetHb) in vitro. The goal of these experiments was to measure the extent of DMTS-induced MetHb formation in vivo. In these experiments, intramuscular (IM) injections of formulated DMTS were administered to mice. Following the IM injection, blood was drawn and analyzed for MetHb using a rapid spectrophotometric method. Methemoglobin levels peaked in a dose-dependent manner between 20 and 30?min., and then began dropping. The highest MetHb levels measured for the 50, 100, 200 and 250?mg/kg doses of DMTS were respectively 3.28, 6.12, 9.69, and 10.76% MetHb. These experiments provide the first experimental evidence that IM administered DMTS generates MetHb in vivo and provide additional evidence for the presence of a secondary therapeutic pathway for DMTS - CN scavenging by DMTS-generated MetHb.     

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

Abstract

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.     

Nondeletional Hb Queens Park [α32(B13)Met→Lys]/Hb H (β4) Disease

A rare nondeletional α-thalassemia-2 (α-thal-2) allele was identified in a Thai boy with Hb H (β4) disease. The proband has α-thal-1 (– –^SEA type) together with a non productive Hb Queens Park (HBA1:c.98T>A) [α32(B13)Met→Lys] α1-globin variant. No abnormal hemoglobin (Hb) fraction was detected by high performance liquid chromatography (HPLC). The clinical effect of this mutation in the proband was comparable to that of deletional α-thal-2 present in Hb H disease.     

Developmental Effect of the XmnI Site on Gγ-Globin Gene Expression Among Newborn Hb F-Malta-I [Gγ117(G19)His→Arg,CAT→CGT] Heterozygotes and Adult β+-Thalassemia Homozygotes

Hb F-Malta-I [^Gγ117(19)His→Arg, CAT→CGT] is a stable and benign variant of Hb F found in 1.8% of Maltese newborn. We studied 120 Hb F-Malta-I heterozygotes and four Hb F‐Malta-I homozygotes. The mean proportion of ^Gγ-F-Malta-I in Hb F was 0.26 ± 0.03 for the Hb F-Malta-I heterozygotes and 0.58 ± 0.06 for the Hb F-Malta-I homozygotes. The Hb F-Malta-I allele was shown to occur on a background of the common Mediterranean haplotype Va [+ + ? ? ? ? ? + + ?]. Furthermore, the common Mediterranean haplotypes Va, IIIb [? + + + ? + + + + ?], I [+ + ? ? ? ? ? + + +] and II [? + ? + + ? + + + +] accounted for most (66.2%) of the wild-type alleles among the tested Hb F-Malta-I heterozygotes.

Different genotypes at the 5′ ? HincII, ^Gγ and ^Aγ HindIII, and 3′ψβ HincII sites (but not at the 5′ ^Gγ XmnI site) were found to be linked to significant variations in the proportion of ^Gγ-F-Malta-I and ^Gγ-globins in the Hb F of newborn Hb F-Malta-I heterozygotes. Moreover, the 5′ ^Gγ XmnI site was found to be associated with variations in Hb F and ^Gγ-globin levels in a population of adult Maltese β-thalassemia (thal) homozygotes. This implies that a determinant linked to the XmnI site which effects ^Gγ-globin gene expression is active in anemic adults but not in normal infants.