Prenatal management of fetal anemia due to pyruvate kinase deficiency: A case report

BACKGROUND

Pyruvate Kinase (PK) deficiency is the most common enzyme defect of glycolysis, leading to congenital hemolytic anemia, which can occur during the neonatal period.

STUDY DESIGN AND METHODS

We report the prenatal management of fetal anemia related to PK deficiency in a family with a severe proband.

RESULTS

The couple had a first child born with hydrops, whose PK deficiency was diagnosed at 18 months of life. He was treated with allogeneic bone marrow transplantation. The second child was free from disease. For the third pregnancy, the amniocentesis revealed a PK deficiency. Weekly ultrasound monitoring of the middle cerebral artery velocity allowed the detection of severe fetal anemia. Two intrauterine red blood cell transfusions (IUTs) were performed, raising the fetal hemoglobin from 6.6 to 14.5 g/dl at 28 weeks' gestation and from 8.9 to 15.3 g/dl at 31 weeks. A hematopoietic stem cell allograft was discussed prenatally but not chosen, as it would not have significantly changed the perinatal prognosis. The patient delivered a 2730 g girl at 37 weeks, with hemoglobin of 13.6 g/dl. The child presented with neonatal jaundice treated with phototherapy and received postnatal transfusions.

DISCUSSION

When a proband is identified in a family, fetal investigation is warranted, to set up third-trimester ultrasound surveillance and perinatal management. In case of fetal severe anemia of unknown etiology, the workup on fetal blood sampling before IUT should comprise the search for erythrocytes enzymopathies, such as PK deficiency. IUTs allow safer full-term delivery in cases with PK deficiency.

HbF-promoting polymorphisms may specifically reduce the residual risk of cerebral vasculopathy in SCA children with alpha-thalassemia

Sickle cell anemia (SCA) is a disease characterized by abnormal red blood cell rheology. Because of their effects on HbS polymerization and red blood cell deformability, alpha-thalassemia and the residual HbF level are known genetic modifiers of the disease. The aim of our study was to determine if the number of HbF quantitative trait loci (QTL) would also favor a specific sub-phenotype of SCA as it is the case for alpha-thalassemia. Our results confirmed that alpha-thalassemia protected from cerebral vasculopathy but increased the risk for frequent painful vaso-occlusive crises. We also showed that more HbF-QTL may provide an additional and specific protection against cerebral vasculopathy but only for children with alpha-thalassemia (-α/αα or -α/-α genotypes).

Clinically relevant updates of the HbVar database of human hemoglobin variants and thalassemia mutations

HbVar (http://globin.bx.psu.edu/hbvar) is a widely-used locus-specific database (LSDB) launched 20 years ago by a multi-center academic effort to provide timely information on the numerous genomic variants leading to hemoglobin variants and all types of thalassemia and hemoglobinopathies. Here, we report several advances for the database. We made clinically relevant updates of HbVar, implemented as additional querying options in the HbVar query page, allowing the user to explore the clinical phenotype of compound heterozygous patients. We also made significant improvements to the HbVar front page, making comparative data querying, analysis and output more user-friendly. We continued to expand and enrich the regular data content, involving 1820 variants, 230 of which are new entries. We also increased the querying potential and expanded the usefulness of HbVar database in the clinical setting. These several additions, expansions and updates should improve the utility of HbVar both for the globin research community and in a clinical setting.

Appropriate thresholds for accurate screening for β-thalassemias in the newborn period: results from a French center for newborn screening

Objectives

Newborn screening (NBS) for β-thalassemia is based on measuring the expression of the hemoglobin A (HbA) fraction. An absence or very low level of HbA at birth may indicate β-thalassemia. The difficulty is that the HbA fraction at birth is correlated with gestational age (GA) and highly variable between individuals. We used HbA expressed in multiples of the normal (MoM) to evaluate relevant thresholds for NBS of β-thalassemia.

Methods

The chosen threshold (HbA≤0.25 MoM) was prospectively applied for 32 months in our regional NBS program for sickle cell disease, for all tests performed, to identify patients at risk of β-thalassemia. Reliability of this threshold was evaluated at the end of the study.

Results

In all, 343,036 newborns were tested, and 84 suspected cases of β-thalassemia were detected by applying the threshold of HbA≤0.25 MoM. Among the n=64 cases with confirmatory tests, 14 were confirmed using molecular analysis as β-thalassemia diseases, 37 were confirmed as β-thalassemia trait and 13 were false-positive. Determination of the optimum threshold for β-thalassemia screening showed that HbA≤0.16 MoM had a sensitivity of 100% and a specificity of 95.3%, whatever the GA.

Conclusions

NBS for β-thalassemia diseases is effective, regardless of the birth term, using the single robust threshold of HbA≤0.16 MoM. A higher threshold would also allow screening for carriers, which could be interesting when β-thalassemia constitutes a public health problem.

Exome sequencing for diagnosis of congenital hemolytic anemia

Background

Congenital hemolytic anemia constitutes a heterogeneous group of rare genetic disorders of red blood cells. Diagnosis is based on clinical data, family history and phenotypic testing, genetic analyses being usually performed as a late step. In this study, we explored 40 patients with congenital hemolytic anemia by whole exome sequencing: 20 patients with hereditary spherocytosis and 20 patients with unexplained hemolysis.

Results

A probable genetic cause of disease was identified in 82.5% of the patients (33/40): 100% of those with suspected hereditary spherocytosis (20/20) and 65% of those with unexplained hemolysis (13/20). We found that several patients carried genetic variations in more than one gene (3/20 in the hereditary spherocytosis group, 6/13 fully elucidated patients in the unexplained hemolysis group), giving a more accurate picture of the genetic complexity of congenital hemolytic anemia. In addition, whole exome sequencing allowed us to identify genetic variants in non-congenital hemolytic anemia genes that explained part of the phenotype in 3 patients.

Conclusion

The rapid development of next generation sequencing has rendered the genetic study of these diseases much easier and cheaper. Whole exome sequencing in congenital hemolytic anemia could provide a more precise and quicker diagnosis, improve patients’ healthcare and probably has to be democratized notably for complex cases.

High fetal hemoglobin level is associated with increased risk of cerebral vasculopathy in children with sickle cell disease in Mayotte

Background

Understanding the genetics underlying the heritable subphenotypes of sickle cell anemia, specific to each population, would be prognostically useful and could inform personalized therapeutics.The objective of this study was to describe the genetic modulators of sickle cell disease in a cohort of pediatric patients followed up in Mayotte.

Methods

This retrospective cohort study analyzed clinical and biological data, collected between January1^st2007 and December 31^st2017, in children younger than 18 years.

Results

We included 185 children with 72% SS, 16% Sβ0-thalassemia and 12% Sβ + thalassemia. The average age was 9.5 years; 10% of patients were lost to follow up. The Bantu haplotype was associated with an increase in hospitalizations and transfusions. The alpha-thalassemic mutation was associated with a decrease of hemolysis biological parameters (anemia, reticulocytes), and a decrease of cerebral vasculopathy. The Single Nucleotide Polymorphisms BCL11A rs4671393, BCL11A rs11886868, BCL11A rs1427407 and HMIP rs9399137 were associated with the group of children with HbF > 10%. Patients with HbF > 10% presented a significant risk of early onset of cerebral vasculopathy.

Conclusions

The most remarkable result of our study was the association of SNPs with clinically relevant phenotypic groups. BCL11A rs4671393, BCL11A rs11886868, BCL11A rs1427407 and HMIP rs9399137 were correlated with HbF > 10%, a group that has a higher risk of cerebral vasculopathy and should be oriented towards the hemolytic sub-phenotype.

Short in-Frame Insertions/Deletions in the Coding Sequence of the α-Globin Gene. Consequences of the 3D Structure and Resulting Phenotypes: Hb Choisy as an Example

A small group of hemoglobin (Hb) variants result from 'in-frame' deletion/insertion (del/ins). We describe a new variant of this group (Hb Choisy), found on the α1 gene, which is the exact counterpart of a previously published deletional variant, Hb J-Biskra [codons 51-58 (or codons 52-59) (-24 bp) (-TCTGCCCAGGTTAAGGGCCACGGC); HBA1: c.157_180del (or HBA2)]. In Hb J-Biskra, the sequence Ser-Ala-Gln-Val-Lys-Gly-His-Gly located from positions α52(E1) to α59(E8) is deleted, while in Hb Choisy the same sequence (Ser-Ala-Gln-Val-Lys-Gly-His-Gly) is inserted at position α52(E1). The variant carrying the insertion appears to be less damaging than the one with the deletion. A possible explanation could be that the additional sequence is located in the C to E interhelical region, and is less disturbing to the general structure of the globin chain. This insertion/deletion (ins/del) is likely favored by the repetition, at an interval of 16 nucleotides, of an eight nucleotide sequence. Comparison of variants of this group, found in the HbVar database, shows that structural modifications resulting from insertions are frequently less damaging than that caused by deletions.

Addressing the diagnostic gaps in pyruvate kinase deficiency: Consensus recommendations on the diagnosis of pyruvate kinase deficiency

Pyruvate kinase deficiency (PKD) is the most common enzyme defect of glycolysis and an important cause of hereditary, nonspherocytic hemolytic anemia. The disease has a worldwide geographical distribution but there are no verified data regarding its frequency. Difficulties in the diagnostic workflow and interpretation of PK enzyme assay likely play a role. By the creation of a global PKD International Working Group in 2016, involving 24 experts from 20 Centers of Expertise we studied the current gaps in the diagnosis of PKD in order to establish diagnostic guidelines. By means of a detailed survey and subsequent discussions, multiple aspects of the diagnosis of PKD were evaluated and discussed by members of Expert Centers from Europe, USA, and Asia directly involved in diagnosis. Broad consensus was reached among the Centers on many clinical and technical aspects of the diagnosis of PKD. The results of this study are here presented as recommendations for the diagnosis of PKD and used to prepare a diagnostic algorithm. This information might be helpful for other Centers to deliver timely and appropriate diagnosis and to increase awareness in PKD.

Prognostic factors of disease severity in infants with sickle cell anemia: A comprehensive longitudinal cohort study

In order to identify very early prognostic factors that can provide insights into subsequent clinical complications, we performed a comprehensive longitudinal multi-center cohort study on 57 infants with sickle cell anemia (55 SS; 2 Sβ°) during the first 2 years of life (ClinicalTrials.gov: NCT01207037). Time to first occurrence of a severe clinical event-acute splenic sequestration (ASS), vaso-occlusive (VOC) event requiring hospitalization, transfusion requirement, conditional/ abnormal cerebral velocities, or death-was used as a composite endpoint. Infants were recruited at a mean age of 4.4 ±1 months. Median follow-up was 19.4 months. During the study period, 38.6% of infants experienced ≥1 severe event: 14% ASS, 22.8% ≥ 1 VOC (median age: 13.4 and 12.8 months, respectively) and 33.3% required transfusion. Of note, 77% of the cohort was hospitalized, with febrile illness being the leading cause for admission. Univariate analysis of various biomarkers measured at enrollment showed that fetal hemoglobin (HbF) was the strongest prognostic factor of subsequent severe outcome. Other biomarkers measured at enrolment including absolute neutrophil or reticulocyte counts, expression of erythroid adhesion markers, % of dense red cells, cellular deformability or ϒ-globin genetic variants, failed to be associated with severe clinical outcome. Multivariate analysis demonstrated that higher Hb concentration and HbF level are two independent protective factors (adjusted HRs (95% CI) 0.27 (0.11-0.73) and 0.16 (0.06-0.43), respectively). These findings imply that early measurement of HbF and Hb levels can identify infants at high risk for subsequent severe complications, who might maximally benefit from early disease modifying treatments.

Maternal consumption of quinine-containing sodas may induce G6PD crises in breastfed children

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect often presenting with neonatal jaundice and/or hemolytic anemia. G6PD hemolytic events are linked with exposure to a pro-oxidant agent. We here report three cases of initial G6PD crises in breastfed children secondary to maternal consumption of a tonic drink which contains quinine. Quinine was found in breast milk of one of the mothers after she consumed tonic water.

CONCLUSION

The amount of quinine that is transmitted through breast milk appears to be sufficient to induce G6PD crises in breastfed children. We hence recommend that consumption of quinine-containing sodas during breastfeeding should be avoided in populations with a high prevalence of G6PD deficiency. What is Known: • G6PD hemolytic events are linked with exposure to a pro-oxidant agent. • Ingestion of fava beans by a mother who was breastfeeding has been reported to induce a neonatal G6PD crisis. What is New: • Maternal consumption of tonic drink which contains quinine appears to be sufficient to induce G6PD crises in breastfed children. • Maternal consumption of quinine-containing sodas during breastfeeding should be avoided in populations with a high prevalence of G6PD deficiency.

Hb Olivet (HBA1: C.40G > A; p.Ala14Thr), a Novel Silent Hemoglobin Variant in Two Families of Distinct Origin

We report two families, members of which are carriers of a novel hemoglobin (Hb) variant that was named Hb Olivet [α13(A11)Ala→Thr (α1) (GCC > ACC); HBA1: c.40G > A; p.Ala14Thr]. The analysis of these cases allowed a clear description of this anomaly that behaves as a silent Hb. In the first family, of Portuguese ethnicity living in France, the proband, a 24-year-old male and his 57-year-old mother, both appeared to be carriers. The son presented with borderline mean corpuscular volume (MCV), while the mother was normocytic and normochromic. Hemoglobin separation on capillary electrophoresis (CE) was normal, while a slightly asymmetric peak was observed on high performance liquid chromatography (HPLC). In a second family, originally from Surinam but living in The Netherlands, the proband, a 6-year-old girl, showed a mild microcytosis at low ferritin levels. The abnormal Hb was inherited from the mother who was clearly iron depleted, was not present in the sister and brother of the proband. The microcytic hypochromic anemia was only shown in two out of a total of four carriers. It therefore seems likely that iron depletion is causative as two carriers are completely normal. Characterization and genotype/phenotype correlation are briefly described.

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.

The genetic basis of asymptomatic codon 8 frame-shift (HBB:c25_26delAA) β(0) -thalassaemia homozygotes

Two 21-year old dizygotic twin men of Iraqi descent were homozygous for HBB codon 8, deletion of two nucleotides (-AA) frame-shift β(0) -thalassaemia mutation (FSC8; HBB:c25_26delAA). Both were clinically well, had splenomegaly, and were never transfused. They had mild microcytic anaemia (Hb 120-130 g/l) and 98% of their haemoglobin was fetal haemoglobin (HbF). Both were carriers of Hph α-thalassaemia mutation. On the three major HbF quantitative trait loci (QTL), the twins were homozygous for G>A HBG2 Xmn1 site at single nucleotide polymorphism (SNP) rs7482144, homozygous for 3-bp deletion HBS1L-MYB intergenic polymorphism (HMIP) at rs66650371, and heterozygous for the A>C BCL11A intron 2 polymorphism at rs766432. These findings were compared with those found in 22 other FSC8 homozygote patients: four presented with thalassaemia intermedia phenotype, and 18 were transfusion dependent. The inheritance of homozygosity for HMIP 3-bp deletion at rs66650371 and heterozygosity for Hph α-thalassaemia mutation was found in the twins and not found in any of the other 22 patients. Further studies are needed to uncover likely additional genetic variants that could contribute to the exceptionally high HbF levels and mild phenotype in these twins.

Haematological determinants of cardiac involvement in adults with sickle cell disease

AIMS

Cardiac involvement is common in sickle cell disease (SCD). Studies are needed to establish haematological determinants of this involvement and prognostic markers. The aim of the study was to identify haematological factors associated with cardiac involvement in SCD and their impact on prognosis.

METHODS AND RESULTS

This longitudinal observational study was performed on 1780 SCD patients with SS or S-β(0)-thalassemia referred to our centre. Six hundred fifty-six met our inclusion criteria (availability of a blood-workup and echocardiogram obtained <1 year apart, no heart valve surgery and no current pregnancy). Median age was 31 (interquartile range, 25-40) years, and median haemoglobin (Hb) was 87 (80-95)g/L. Left ventricular (LV) dilation, left atrial dilation, cardiac index (CI) >4 L/min/m(2), LV ejection fraction <55%, and tricuspid regurgitant velocity (TRV) ≥2.5 m/s were found in 35, 78, 23, 8.5, and 17% of patients, respectively. Compared with other patients, those in the fourth quartiles (Q4) of LV end-diastolic dimension index (LVEDDind) and left atrial dimension index (LADind) and those with high CI had significantly lower Hb, % foetal Hb (HbF), and red blood cell (RBC) counts; and significantly higher lactate dehydrogenase, bilirubin, and %dense RBCs. Independent haematologic determinants of Q4 LVEDDind and LADind were low RBC count and %HbF; high %dense RBCs were associated with LADind. Low %HbF and RBC count were associated with high CI. High %dense RBCs or no α-thalassemia gene deletion was associated with greater severity of anaemia and cardiac dilation and with higher CI. During the median follow-up of 48 (32-59) months, 50 (7.6%) patients died. Tricuspid regurgitant velocity ≥ 2.5 m/s was a predictor of mortality. The risk of death increased four-fold when left ventricular ejection fraction <55% was present also (P = 0.0001).

CONCLUSION

Cardiac dilation and CI elevation in patients with SCD are associated with haematologic variables reflecting haemolysis, RBC rigidity, and blood viscosity. Tricuspid regurgitant velocity ≥ 2.5 and LV dysfunction (even mild) predict mortality.

[Symptomatic extramedullary haematopoiesis in β-thalassemia: A retrospective single centre study]

INTRODUCTION

Symptomatic extramedullary hematopoiesis (EH) is a rare but potentially severe phenomenon which occurs in β-thalassemia. There are no treatment guidelines.

METHODS

Retrospective single centre study including the cases of symptomatic EH encountered between 1997 and 2014 in a unit specialised in red blood cell genetic disorders. Description of clinical, biological and radiological characteristics of the patients, treatments received, and outcomes.

RESULTS

Among 182 β-thalassemia patients followed during the study period, 7 cases of symptomatic EH were diagnosed. They were 5 men and 2 women, and their mean age was 37 years. Four patients were splenectomised, two patients were regularly transfused, and four patients had already received erythropoietin. EH was localised in intravertebral areas and responsible for dorsal spinal cord compression in 5 patients, in paravertebral dorsal area in 1 patient, and in presacral area in 1 patient. The mean hemoglobin level at diagnosis was 7.9 g/dL. Treatment administered included: red cell transfusion in 6 cases, associated with hydroxyurea in 5 cases and/or radiotherapy in 3 patients. One patient was treated with surgery and HU. After a median follow-up of 41 months, clinical recovery was complete in 2 patients and partial in 5 patients.

CONCLUSION

EH must be suspected in β-thalassemia in patients presenting clinical signs of organ compression, and a typical radiological aspect. The functional prognosis depends on the rapidity of treatment, which includes red blood cell transfusion, hydroxyurea, radiotherapy, and rarely surgery. Long-term outcome is uncertain.

A genetic score for the prediction of beta-thalassemia severity

Clinical and hematologic characteristics of beta(β)-thalassemia are determined by several factors resulting in a wide spectrum of severity. Phenotype modulators are: HBB mutations, HBA defects and fetal hemoglobin production modulators (HBG2:g.-158C>T polymorphism, HBS1L-MYB intergenic region and the BCL11A). We characterized 54 genetic variants at these five loci robustly associated with the amelioration of beta-thalassemia phenotype, to build a predictive score of severity using a representative cohort of 890 β-thalassemic patients. Using Cox proportional hazard analysis on a training set, we assessed the effect of these loci on the age at which patient started regular transfusions, built a Thalassemia Severity Score, and validated it on a testing set. Discriminatory power of the model was high (C-index=0.705; R(2)=0.343) and the validation conducted on the testing set confirmed its predictive accuracy with transfusion-free survival probability (P<0.001) and with transfusion dependency status (Area Under the Receiver Operating Characteristic Curve=0.774; P<0.001). Finally, an automatized on-line calculation of the score was made available at http://tss.unica.it. Besides the accurate assessment of genetic predictors effect, the present results could be helpful in the management of patients, both as a predictive score for screening and a standardized scale of severity to overcome the major-intermedia dichotomy and support clinical decisions.

Characterization of two unique α-globin gene cluster deletions causing α-thalassemia in Israeli Arabs

The molecular basis of α-thalassemia (α-thal) is complex. The use of multiplex ligation-dependent probe amplification (MLPA) has offered the possibility of identifying more gene deletions causing α-thal. Our objective was to determine the molecular basis of two patients with Hb H (β4) disease. By using MLPA in combination with comparative genomic hybridization (CGH) we identified two novel α-globin gene cluster deletions: a 30 kb deletion (patient 1) we refer to as - -(JAL) and a large 216 kb deletion (patient 2) we refer to as - -(LOD). Patient 1 was a compound heterozygote for - -(JAL) and -α(3.7) (rightward deletion). Twelve family members of patient 1 carrying the - -(JAL) deletion were available for evaluation: five with - -(JAL)/-α(3.7), four with - -(JAL)/α(Hph I)α and three with - -(JAL)/αα. Their clinical picture of compound heterozygosity was compatible with moderate Hb H disease. In patient 2 (- -(LOD)/-α(3.7)), no additional symptoms were present despite the heterozygous deletion of seven known genes, three non coding RNAs (ncRNAs), four unknown genes and two pseudo genes. Further analysis of more patients with α-thal deletions will have implications for genetic counseling and appropriate therapy.

Hemolytic anemia and progressive neurologic impairment: think about triosephosphate isomerase deficiency

We have reported the first Tunisian case of triosephosphate isomerase (TPI) deficiency in a 2-year-old girl. She was the first child of a nonconsanguineous couple. The disease included a neonatal onset of chronic hemolytic anemia, recurrent low-respiratory infections then progressive neurological involvement. The diagnosis was made after her death from the TPI values of her parents who exhibited intermediate enzyme deficiency. Molecular study of TPI genes showed that the father and the mother are heterozygous for Glu105Asp mutation. Pediatricians must be alert to the differential diagnosis in patients having hemolytic anemia and other concomitant manifestations.

Comprehensive functional annotation of 18 missense mutations found in suspected hemochromatosis type 4 patients

Hemochromatosis type 4 is a rare form of primary iron overload transmitted as an autosomal dominant trait caused by mutations in the gene encoding the iron transport protein ferroportin 1 (SLC40A1). SLC40A1 mutations fall into two functional categories (loss- versus gain-of-function) underlying two distinct clinical entities (hemochromatosis type 4A versus type 4B). However, the vast majority of SLC40A1 mutations are rare missense variations, with only a few showing strong evidence of causality. The present study reports the results of an integrated approach collecting genetic and phenotypic data from 44 suspected hemochromatosis type 4 patients, with comprehensive structural and functional annotations. Causality was demonstrated for 10 missense variants, showing a clear dichotomy between the two hemochromatosis type 4 subtypes. Two subgroups of loss-of-function mutations were distinguished: one impairing cell-surface expression and one altering only iron egress. Additionally, a new gain-of-function mutation was identified, and the degradation of ferroportin on hepcidin binding was shown to probably depend on the integrity of a large extracellular loop outside of the hepcidin-binding domain. Eight further missense variations, on the other hand, were shown to have no discernible effects at either protein or RNA level; these were found in apparently isolated patients and were associated with a less severe phenotype. The present findings illustrate the importance of combining in silico and biochemical approaches to fully distinguish pathogenic SLC40A1 mutations from benign variants. This has profound implications for patient management.

A One-Step Real-Time PCR Assay for Rapid Prenatal Diagnosis of Sickle Cell Disease and Detection of Maternal Contamination

INTRODUCTION

Mutations at the codon 6 of the beta-globin gene (hemoglobin [Hb] S and HbC) can be routinely identified by various methods and prenatal diagnosis has been available to affected families for several years. However, the presence of maternal cells in fetal samples constitutes a serious potential source of prenatal misdiagnosis and most methods currently used to detect maternal contamination are based on the analysis of highly polymorphic loci. In addition, these methods are labor intensive and time consuming and risk carry-over contamination.

METHOD

We describe here a one-step method for mutation detection that uses fluorescent hybridization probes with melting curve analysis for both simultaneously prenatal diagnosis of sickle cell disease and potential maternal contamination.

RESULTS

Retrospective and prospective prenatal diagnosis studies (conducted in 20 and 50 cases, respectively), using both the regular procedure and real-time PCR assay show perfect concordant results. We show in addition, that as little as 5% maternal contamination can be detected and that genotype determinations are unambiguous.

Estimation of the difference in HbF expression due to loss of the 5' δ-globin BCL11A binding region

BCL11A was the focus of recent studies on its inhibiting effect when bound onto the β-globin cluster in the mechanism of hemoglobin switching and HbF downregulation. We examined a cohort of 10 patients displaying different HbF levels and short deletions within the γβ-δ intergenic region to find a possible correlation with the BCL11A binding site located 5' to the δ-globin gene. Precise characterization of deletions was achieved using a custom DNA-array chip and breakpoint sequencing. The α-globin cluster and major SNP associated with HbF expression were genotyped. Our results show that the loss of the BCL11A binding domain located 5' to the δ-globin gene is correlated with a strong HbF difference (mean+2.7 g/dL, ratio 2.81). This result provides evidence for the use of BCL11A level down-regulation or this domain blockage for new therapies in sickle cell disease and β-thalassemia major patients.

Practical approach for characterization of glucose 6-phosphate dehydrogenase (G6PD) deficiency in countries with population ethnically heterogeneous: description of seven new G6PD mutants

We present a rapid strategy based on Restriction Fragment Length Polymorphism (RFLP) analysis to characterize the more frequent glucose 6-phosphate dehydrogenase (G6PD) variants observed in a population with high gene flow. During a study involving more than 600 patients, we observed mainly G6PD A(-) (c.202G>A, c.376A>G; p.Val68Met, p.Asn126Asp), G6PD Mediterranean (Med) (c.563C>T, p.Ser188Phe), and G6PD Betica (c.376A>G, 542A>T; p.126Asn>Asp, 181Asp>Val) with addition of a few rare ones. A number of 10 abnormalities amounted to 92% of all the molecular defects. In addition, seven new mutations were found: three presented with acute hemolytic anemia following oxidative stress [G6PD Nice (c.1380G>C, p.Glu460Asp), G6PD Roubaix (c.811G>C, p.Val271Leu), and G6PD Toledo (c.496C>T, p.Arg166Cys)], three with different degrees of chronic hemolytic anemia [G6PD Lille (c.821A>T, p.Glu274Val), G6PD Villeurbanne (c.1000_1002delACC, p.Thr334del), and G6PD Amiens (c.1367A>T, p.Asp456Val)] and one found fortuitously G6PD Montpellier (c.1132G>A, p.Gly378Ser).

First reported case of prenatal diagnosis for pyruvate kinase deficiency in a Chinese family

We describe the first case of prenatal diagnosis for pyruvate kinase (PK) deficiency in Chinese and emphasize that this disease is an important differential diagnosis in pediatric patients with non-spherocytic hemolytic anemia. A Han Chinese child with a history of severe transfusion-dependent hemolytic anemia was diagnosed to have PK deficiency. Prenatal diagnosis was performed on the second child based on the genetic findings from the family. The index patient was compound heterozygous for a missense mutation (c.1073G > A. p.Gly358Glu) from his father and a large deletion (c.283 + 1914_c.1434del5006) from his mother. The fetus was a simple heterozygote for the paternal mutation. Pregnancy was allowed to continue and a healthy baby was born. Severe PK deficiency warranting prenatal diagnosis is seen in Han Chinese. Genetic characterization and genotype-phenotype correlation studies on PKLR in different populations are indicated to better define the role of prenatal diagnosis in PK deficiency.

Variants in genetic modifiers of β-thalassemia can help to predict the major or intermedia type of the disease

A cohort of 106 patients included in the French National Registry for Thalassemia were genotyped for 5 genetic modifiers of severity: i) β-thalassemia mutations; (ii) the XmnI SNP; (iii) the -3.7 kb α-thal deletion; (iv) the tag-SNP rs 11886868 in BCL11A exon 2; and (v) the tag-SNP rs9399137 in the HBSB1L-cMYB inter-region. Multivariate analysis was performed to study the risk of thalassemia Intermedia phenotype associated with the different combinations of alleles. The presence or absence of the favorable alleles could accurately predict the type of thalassemia in 83.2% of the cases. The percentage of correct predictions made from the β-thalassemia mutations and the XmnI SNP alone were significantly improved by the adjustment with the 3 other modifiers; from 73.6% to 83.2% (P<0.001). In this study, we showed that predictions based on genetic modifiers can foresee the Major or Intermedia type of β-thalassemia, even in cohorts of patients with various β-globin genotypes.

Evaluation of the free α-hemoglobin pool in red blood cells: a new test providing a scale of β-thalassemia severity

β-Thalassemias are characterized by an imbalance of globin chains with an excess of α-chains which precipitates in erythroid precursors and red blood cells (RBCs) leading to inefficient erythropoiesis. The severity of the disease correlates with the amount of unpaired α-chains.Our goal was to develop a simple test for evaluation of the free α-hemoglobin pool present in RBC lysates. Alpha-Hemoglobin Stabilizing Protein (AHSP), the chaperone of α-Hb, was used to trap excess a-Hb. A recombinant GST-AHSP fusion protein was bound to an affinity micro-column and then incubated with hemolysates of patients. After washing, the α-Hb was quantified by spectrophotometry in the elution fraction. This assay was applied to 54 patients: 28 without apparent Hb disorder, 20 β-thalassemic and 6 α-thalassemic. The average value of free α-Hb pool was 93 ± 21 ppm (ng of free α-Hb per mg of Hb subunits)in patients without Hb disorder, while it varies from 119 to 1,756 ppm, in β-thalassemic patients and correlated with genotype. In contrast,the value of the free α-Hb pool was decreased in α-thalassemic patients (65 ± 26 ppm). This assay may help to characterize β-thalassemia phenotypes and to follow the evolution of the globin chain imbalance(α/β+γ ratio) in response to treatment.