Hb Boskoop [HBA2c.112C>T p.Pro38Ser]: a new α2 chain variant observed in a Morrocan family

We describe a new nondeletional α-thalassemia (α-thal) determinant found in a Moroccan infant and in two members of his family. The new mutation generates an abnormal hemoglobin (Hb) as a consequence of a Pro→Ser amino acid substitution at codon 37 (old nomenclature) of the α2 gene. The new Hb variant is barely separable on high performance liquid chromatography (HPLC) but the expression of the α chain mutant measured on reversed phase chromatography is one-third of that expected from a stable α2 variant, which explains the mild α-thal phenotype observed in the carriers. As shown for other mutations described in our laboratory (i.e., Hb Gouda), this variant could also be common in the North African population, overlooked because of the mild phenotype and silent behavior on HPLC. Nevertheless, these silent variants could generate intermediate Hb H diseases in association with Mediterranean α(0)-thal deletion defect.     

Hb Lake Tapawingo [α46(CE4)Phe→Ser; HBA2:c.140T>C]: a new unstable α chain hemoglobin variant associated with low systemic arterial saturation

A new unstable α-globin variant was detected in a child with hypoxemia and anemia. The child's mother was found to carry the same mutation. The hemoglobin (Hb) variant co-eluted with Hb A(2) by cation exchange high performance liquid chromatography (HPLC) and appeared cathodal to Hb A and anodal to Hb F by isoelectric focusing. It represented less than 20% of the total Hb and was unstable by isopropanol testing. Gene sequencing identified a missense mutation on the α2 gene [HBA2:c.140T>C]. Oxygen dissociation and P(50) test results were normal.     

Hb Cambridge-MA [β144(HC1)-β146(HC3)Lys-Tyr-His→0 (HBB c.433 A>T)]: a new high oxygen affinity variant

A new β hemoglobin (Hb) variant, Hb Cambridge-MA [β144(HC1)β146(HC3)Lys-Tyr-His→0 (AAG>TAG) (HGVS: HBB c.433 A>T] is described. The variant was characterized by high performance liquid chromatography (HPLC), alkaline, acid, globin chain and capillary electrophoresis, isoelectric focusing (IEF), heat and isopropanol stability, p50 analyses, intact globin mass spectrometry (MS) and DNA sequencing. The new variant shows high oxygen (O?) affinity and is associated with mild polycythemia.     

Hb Nile[A1] and Hb Nile[A2]: Novel Identical [α77(EF6)Pro→Ser] Variants Found in Either the α1- or α2-Globin Genes

We describe a novel hemoglobin (Hb) variant, caused by a CCC > TCC transition at codon 77 on the α gene. The mutation was found in two unrelated patients, in one patient on the α1 gene and in the other patient on the α2 gene. Both are anemic patients of African origin. Due to the neutral Pro→Ser substitution, Hb Nile could not be separated from Hb A with common short-run screening methods for high performance liquid chromatography (HPLC) and capillary electrophoresis, but was evidently present after prolonged cation exchange HPLC or separation by isoelectric focusing (IEF). Reversed phase HPLC separation of the globin chains revealed the normal and abnormal α chains with an expression of about 20% for Hb Nile[A1], indicative of normal expression and stability of the mutant protein.     

A Novel α2-Globin Gene Mutation: Hb Debao [α31(B12)Arg→Trp; HBA2: c.94A>T]

We report a novel mutation on the α2-globin gene, Hb Debao [α31(B12)Arg→Trp; HBA2: c.94A>T] detected in a Chinese family. This mutation gives rise to a previously undescribed hemoglobin (Hb) variant that was undetectable by electrophoretic or chromatographic methods. Hb Debao was associated with an α⁺-thalassemia (α⁺-thal) deletion [?α^3.7 (rightward)] producing a mild phenotype with significant microcytosis and hypochromia, while the combination of this mutation with an α⁰-thal deletion (??^SEA) resulting in a severe form of Hb H (β4) disease, which is consistent with a thalassemic phenotype associated with the novel mutation.     

Hb Phimai [β72(E16)Ser→Thr]: a novel β-globin structural variant found in association with Hb constant spring in pregnancy

A Thai pregnant woman with α and β hemoglobinopathies is described. Initial hemoglobin (Hb) analysis revealed an unknown variant with a high performance liquid chromatography (HPLC) elution pattern similar to Hb Hope [β136(H14)Gly→Asp]. Subsequent DNA-based diagnostics revealed that she was a carrier of Hb Constant Spring [Hb CS, α142, TAA>CAA (α2)] and a novel β-globin chain variant [β72(E16)Ser→Thr, AGT>ACT] which we named Hb Phimai. Her hematological findings and a simple DNA test for differential diagnosis of Hb Phimai and Hb Hope are presented.     

Hb Cemenelum [α92 (FG4) Arg→Trp]: A hemoglobin variant of theα1/β2 interface that displays a moderate increase in oxygen affinity

Summary Hb Cemenelum [92 (FG4) ArgTrp] carries a structural modification at the same position as Hb Chesapeake, a very high oxygen affinity variant. Hb Cemenelum was found in a French diabetic patient with no abnormal hematological features. The purified abnormal hemoglobin, like Hb J Cape Town, another variant of position 92(FG4), displayed only a 1.5-to 2-fold increased oxygen affinity and a reduced cooperativity. This hemoglobin demonstrates that, even for some key residues of the1/2 interface, the degree at which the functional properties are altered depends upon the specific residue occupying this position.     

A new β chain hemoglobin variant with increased oxygen affinity: Hb Santa Giusta Sardegna [β93(F9)Cys→Trp; HBB c.282T>G

During a screening program for the identification of β-thalassemia (β-thal) carriers in Sardinia, Italy, we identified two subjects with increased hemoglobin (Hb) levels and an abnormal Hb variant. The same variant was detected in a family member. DNA sequencing revealed a TGT > TGG mutation at codon 93 of the β-globin gene. Structural analysis demonstrated that the cystine residue at position 93 of the β chain was substituted by tryptophan. Since this amino acid substitution had not yet been reported, we designated this variant Hb Santa Giusta Sardegna for the place of birth of the subjects. This amino acid substitution occurs at the tyrosine pocket of the β chain as well as at the α1β2/α2β1 contact of the quaternary structure of the molecule. The presence of this Hb in the hemolysate causes an increased oxygen affinity, a slightly reduced Bohr effect and a reduced heme-heme interaction (n(50), Hill's constant) in comparison with those of Hb A.     

Hb La Coruña [beta38(C4)Thr-->Ile]: a new hemoglobin variant leading to familial polycythemia

Hb La Coru?a [beta38(C4)Thr --> Ile] is a new hemoglobin (Hb) variant that has an increased oxygen affinity. Clinically, this Hb leads to erythrocytosis. Hb La Coru?a is an electrophoretically silent variant that can be detected by reversed phase high performance liquid chromatography (HPLC) and characterized by DNA sequencing. The patient was a 22-year-old Spanish male whose family lived in La Coru?a, in the northwest of Spain. His mother was also a carrier.     

Neonatal cyanosis due to a new (G)γ-globin variant causing low oxygen affinity: Hb F-Sarajevo [(G)γ102(G4)Asn→Thr, AAC>ACC

A baby girl, born at term, presented with severe cyanosis and received oxygen supplementation. Consecutive arterial blood gas analysis showed a pronounced right shift of the saturation curve, suggesting the presence of a hemoglobin (Hb) variant. A new (G)γ-globin variant was detected, namely HBG2:c.308G, which we have named Hb F-Sarajevo, the city from where the baby's parents originate. This A to C transversion exists in cis to the common (A)γ(T) and the resulting mutant Hb molecule exhibits very low oxygen affinity and cooperativity. Its analogue in the β-globin gene is Hb Kansas [β102(G4)Asn→Thr, AAC>ACC].     

Two New Hemoglobin Variants: Hb Tallahassee [α3(A1)Ser→Tyr; HBA2: c.11C>A] and Hb Madison-NC [β119(GH2)Gly→Ser; HBB: c.358G>A]

Of the 1570 reported hemoglobin (Hb) variants detected to date, 390 are α2-globin chain (some variants have yet to be identified by DNA analyses and are therefore presumed) and 827 are the result of mutations of the β-globin chain. Due to their location on the Hb structure, only a minority of these variants result in a clinical phenotype; most are silent and are detected during routine surveillance, are found incidentally during other disease-related investigations or following newborn screening programs. In this report we discuss phenotype/genotype and molecular characteristics of two new Hb variants, both of which were clinically silent. One is an α2-globin chain variant located at codon 3 [α3(A1)Ser→Tyr; HBA2: c.11C?>?A] named Hb Tallahassee and the other is a β-globin chain variant located at codon 119 [β119(GH2)Gly→Ser; HBB: c.358G?>?A] called Hb Madison-NC.     

A new Unstable α2‐Globin Gene Variant: Hb Chartres [α33(B14)Phe→Ser]

Hb M Akita disease is a cyanotic hemoglobinopathy found in Akita Prefecture, Japan. The abnormal hemoglobin was found to be the same as Hb M Hyde Park (692 His → Tyr) by chemical analysis in 1967. In this disease signs of accelerated hemolysis (serum bilirubin, 2.4 mg/dl; splenomegaly, 2 finger breadths; Hb, 10.7 g/dl; reticulocyte index, 2.7) were noted, but the causes of its slight anemia were revealed to be fairly complex by ferrokinetic study, RBC life-span measurement, and ^mTc myeloscintigram.

The anemia in this disease is caused not only by shortened erythrocyte survival (T 1/2 = 11.5 days by ⁵¹Cr-tagging method) and sequestration of red cells in the spleen (Spleen: liver ratio = 2.5 ～ 3.0 by ⁵¹Cr-surface counting), hut also by slow supply of erythro-cytes to the peripheral blood from the bone marrow, presumably, related to the existence of unstable Hb M Akita and its derivative (Hb Akita) in the erythroid cells. Both Carrell's isopropanol test and Heinz body formation test were positive. In spite of maximally increased total erythropoiesis (8 times as high as the normal level; M:E ratio = 0.22:1.0), supply of red cells from the bone marrow to the peripheral blood was significantly decreased. The distribution of hemato-poietic sites throughout the body was reasonably uniform.     

Hb G-Waimanalo [A1] [α64(E13)Asp→Asn; HBA1: c.193 G > A] with Decreased Oxygen Affinity

Abstract

A clinically asymptomatic 12-year-old girl showed microcytosis in routine examination. Cation exchange high performance liquid chromatography (HPLC), revealed two additional peaks eluting after Hb A and DNA sequencing uncovered a novel heterozygous mutation at codon 64 of the α1-globin gene. The hemoglobin (Hb) variant was annotated as Hb G-Waimanalo [A1]. Further analyses demonstrated a decreased oxygen affinity Hb compared to the normal Hb configuration.     

Identification of a New HBA1 Gene Mutation (HBA1:c.301-2A>T) in Cis with Hb Riccarton (HBA1:c.154G>A) [α51(CE9)Gly→Ser

We report two point mutations found in a heterozygous state on the HBA1 gene of an 88-year-old Argentinean patient with an α(+)-thalassemia (α(+)-thal) phenotype: Hb Riccarton HBA1:c.154G>A) [α51(CE9)Gly→Ser] and a novel mutation, HBA1:c.301-2A>T that affects the splicing acceptor site of the second intron and leads to a non functional α-globin chain. Cloning of the HBA1 PCR (polymerase chain reaction) product and direct sequencing of the clones revealed that both mutations were in cis.     

Hb Savaria [α49(CE7)Ser→Arg; HBA2: c.150C > A]: A New Case and Complete Description

Hb Savaria [α49(CE7)Ser→Arg; HBA2: c.150C?>?A] is a rare hemoglobin (Hb) variant, initially described in Eastern Europe but present worldwide. It belongs to that class of variants which can be confused with Hb S [β6(A3)Glu→Val; HBB: c.20A?>?T] by automated protein analysis and thus needs special tests for proper identification. Because it could arise from different nucleotide substitutions and according to the rules of the Human Genome Variation Society (HGVS) nomenclature, three ‘Hb Savaria’ variants are possible. In the case reported here it resulted from the HBA2: c.148A?>?C change.     

Description of the Phenotypes of 63 Heterozygous,Homozygous and Compound Heterozygous Patients Carrying the Hb Groene Hart [α119(H2)Pro→Ser; HBA1: c.358C>T] Variant

We here report the phenotypes and genotypes of 63 patients of North African origin, carriers of Hb Groene Hart [Hb GH, α119(H2)Pro?→?Ser; HBA1: c.358C>T], an α⁺-thalassemia (α⁺-thal) hemoglobin (Hb) variant. Fifty patients were heterozygous, five were homozygous and eight also carried the common ?α^3.7 (rightward) deletion in compound heterozygosity. The expression of the α^GH-globin chain is increased in the following order: heterozygous, compound heterozygous and homozygous. Parallel significant changes of mean corpuscular Hb (MCH) and mean corpuscular volume (MCV) were also observed. Our large cohort of Hb GH carriers could have been obtained by the systematic realization of globin chain separation by reversed phase liquid chromatography (RP-LC) in our routine Hb testing.     

A Case Series of α-Thalassemia Intermedia Due to Compound Heterozygosity for Hb Adana [HBA2: c179G>A (or HBA1); p.Gly60Asp] With Other α-Thalassemias in Malay Families

Hb Adana [HBA2: c179G>A (or HBA1); p.Gly60Asp] is a rare hemoglobin (Hb) variant due to a mutation at codon 59 of the α2- or α1-globin gene resulting in a glycine to aspartic acid substitution. Two siblings with a unique coinheritance of Hb Adana and Hb Constant Spring (Hb CS, α142, Term→Gln, TAA>CAA; HBA2: c.427?T>C) (α^{codon 59}α/α^CSα), were compared phenotypically with another two siblings carrying the Hb Adana mutation and a 3.7?kb deletion (α^{codon 59}α/?α^3.7). Although they all had α-thalassemia intermedia (α-TI), the former were clinically more severe than the latter. The first pair of siblings presented at a much younger age than the second pair and showed lower Hb levels and significant extramedullay hemopoiesis. Another case of a hydropic fetus as a result of Hb H/Hb Adana is also described. Their clinical phenotypes and hematological parameters are all presented for comparison.     

Hb Grifton [α87(F8)His→Pro; HBA1: C.263A > C (or HBA2)] Causes Abnormal Pulse Oximetry Measurements

An asymptomatic toddler and his mother consistently demonstrated low transcutaneous pulse oximetry (SpO2) measurements, discordant with normal arterial blood gas analyses while breathing room air. Previous evaluations by medical teams were unable to identify an etiology of their perceived hypoxia. Further investigation revealed that the boy carried an abnormal variant, Hb Grifton or α87(F8)His→Pro; HBA1: c.263A?>?C (or HBA2), discovered on newborn screening, which was not suspected as the underlying cause of his abnormal pulse oximetry readings until an inpatient admission to our hospital for asymptomatic “hypoxia,” where he was found to share these same characteristics with his mother. We showed that a difference in light absorption between the oxygenated Hb Grifton variant and oxygenated Hb A resulted in erroneous pulse oximetry values. This phenomenon has previously been reported in a handful of other variant Hbs. Astute clinical suspicion, in conjunction with laboratory testing leading to correct diagnoses of variant Hbs, may prevent expensive work-ups and unnecessary medical treatments for asymptomatic patients falsely presumed to be hypoxemic based on low pulse oximetry measurements.