Clinical and haematological data in 254 cases of beta-thalassaemia trait in Italy

The impact of the UGT1A1*60 allele on bilirubin serum concentrations

AIM

Identify the functional status of the uridine-diphosphate glucuronyl transferase 1A1 (UGT1A1) -3279T>G (*60) variant.

MATERIALS & METHODS

Retrospective review of clinically obtained serum bilirubin concentrations in pediatric patients to evaluate the association of the UGT1A1 -3279T>G (*60) variant with bilirubin concentrations and assessed linkage disequilibrium of the UGT1A1 -3279T>G (*60) and A(TA)7TAA (*28) variants.

RESULTS

Total bilirubin concentration did not differ between patients who had a UGT1A1*1/*1 diplotype and patients homozygous for the UGT1A1 -3279T>G (*60/*60) variant. Total bilirubin concentration was lower in patients homozygous for the UGT1A1 -3279T>G (*60/*60) variant than in patients homozygous for the UGT1A1 A(TA)7TAA (*28/*28) variant (p < 0.01). The -3279T>G (*60) and A(TA)7TAA (*28) variants were in strong incomplete linkage disequilibrium in both black and white patients.

CONCLUSION

The presence of the UGT1A1 -3279T>G (*60) variant is not associated with increased bilirubin concentrations.

Iron metabolism in heterozygotes for hemoglobin E (HbE), alpha-thalassemia 1, or beta-thalassemia and in compound heterozygotes for HbE/beta-thalassemia

BACKGROUND

Despite large populations carrying traits for thalassemia in countries implementing universal iron fortification, there are few data on the absorption and utilization of iron in these persons.

OBJECTIVE

We aimed to determine whether iron absorption or utilization (or both) in women heterozygous for beta-thalassemia, alpha-thalassemia 1, or hemoglobin E (HbE) differed from that in control subjects and compound HbE/beta-thalassemia heterozygotes.

DESIGN

In Thai women (n = 103), red blood cell indexes, iron status, non-transferrin-bound iron, and growth differentiation factor 15 were measured, and body iron was calculated. Fractional iron absorption was measured from meals fortified with isotopically labeled ((57)Fe) Fe sulfate, and iron utilization was measured by the infusion of ((58)Fe) Fe citrate.

RESULTS

Iron utilization was approximately 15% lower in alpha-thalassemia 1 or beta-thalassemia heterozygotes than in controls. When corrected for differences in serum ferritin, absorption was significantly higher in the alpha- and beta-thalassemia groups, but not the HbE heterozygotes, than in controls. HbE/beta-thalassemia compound heterozygotes had lower iron utilization and higher iron absorption and body iron than did controls. Nontransferrin-bound iron and growth differentiation factor 15 were higher in the compound heterozygotes, but not in the other groups, than in the controls.

CONCLUSIONS

In alpha-thalassemia 1 and beta-thalassemia heterozygotes with ineffective erythropoesis, dietary iron absorption is not adequately down-regulated, despite a modest increase in body iron stores. In populations with a high prevalence of these traits, a program of iron fortification could include monitoring for possible iron excess and for iron deficiency.

Is the beta thalassaemia trait of clinical importance?

Although the beta thalassaemia trait affects millions of people worldwide, there have been no controlled studies to determine whether it is associated with any clinical disability or abnormal physical signs. To address this question, 402 individuals were studied: 217 with beta thalassaemia trait, of whom 154 were aware of the diagnosis and 63 were unaware until after the completion of the study; 89 normal controls; and 96 controls with mild hypochromic anaemia. There was a significant increase in symptoms ascribable to anaemia and episodes of pyrexia in those with the beta thalassaemia trait that were not influenced by prior knowledge that they had this condition. There was no difference in physical findings, notably splenomegaly, between those with beta thalassaemia trait and either control group.

A post-transcriptional process contributes to efficient gamma-globin gene silencing in definitive erythroid cells

OBJECTIVES

The expression of human gamma globin is developmentally regulated through mechanisms that affect the transcriptional activity of its encoding gene. The current manuscript investigates whether the efficiency of this process might be enhanced though an unrecognized post-transcriptional event that defines the stability of gamma-globin mRNA.

METHODS

Experiments were conducted in vivo in transgenic mice expressing human gamma globin in their adult erythroid cells. The expression of gamma-globin protein was manipulated by breeding the transgene into animals producing different levels of endogenous mouse beta-globin. Changes in the expression of gamma globin were then correlated to measures of gamma-globin mRNA stability in vivo.

RESULTS

Human gamma globin was expressed at higher levels in thalassemic than in than non-thalassemic control transgenics, paralleling a highly significant increase in the stability of gamma-globin mRNA. Other molecular events-including possible transcriptional induction of the transgene, or an increase in the stability of the gamma-globin protein-did not appear to contribute to the observed increase in transgene expression. As anticipated, the stability of gamma-globin mRNA also fell in bitransgenic animals that co-expressed human beta-globin mRNA.

CONCLUSIONS

Our results are consistent with a model for dynamic post-transcriptional control of gamma-globin gene expression, through modulation of the stability of its encoding mRNA. Moreover, the stability of gamma-globin mRNA appears to be inversely related to ambient levels of co-expressed beta-globin mRNA. This data suggests that therapeutic gene-reactivation and/or gene-replacement therapies may be particularly effective in individuals with severe forms of beta-thalassemia.

Plasma kinetics of a cholesterol-rich microemulsion in subjects with heterozygous beta-thalassemia

Patients with beta-thalassemia trait have been reported to present lower plasma concentrations of low-density lipoprotein (LDL) and lower frequencies of acute myocardial infarction than normal subjects. In this study, the metabolism of LDL was tested in 12 patients with heterozygous beta-thalassemia trait (HBT) and 13 healthy subjects without the disease by determining the plasma kinetics of an artificially made cholesterol-rich microemulsion (LDE) that mimics the LDL metabolism and binds to LDL receptors. The emulsion was labeled with 14C-cholesterol ester and injected intravenously into the subjects. Blood samples were drawn at regular intervals over 24 hr to determine the plasma decay curve of the emulsion radioactive label and to estimate its plasma fractional clearance rate (FCR, in hr(-1)). FCR of the 14C-cholesterol ester was greater in HBT compared to controls (0.0631 +/- 0.0178 hr(-1) and 0.0501 +/- 0.0094 hr(-1), respectively; mean +/- SD, P = 0.022). No differences were found regarding LDL cholesterol plasma concentration between the two groups, but apolipoprotein B concentration was lower in HBT than in control subjects (80 +/- 44 and 96 +/- 14, respectively; mean +/- SD, P = 0.026). Our results show that LDE FCR is increased in HBT, indicating that LDL clearance is increased in patients with beta-thalassemia trait possibly due to the increased proliferation in the bone marrow of erythroid precursors.

Heterocellular hereditary persistence of fetal haemoglobin affects the haematological parameters of beta-thalassaemia trait

To assess and define the effects of heterocellular hereditary persistence of fetal haemoglobin (HPFH) on the haematological phenotype of heterozygous beta-thalassaemia, we have studied a large kindred that included a total of 204 subjects with 60 beta-thalassaemia carriers, of whom 35 were also heterozygous, and five homozygous, for heterocellular HPFH. The study was possible because of the homogeneity of the beta-thalassaemia mutation and the ability to genotype the heterocellular HPFH allele. Heterocellular HPFH had a significant effect on the mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV) and haemoglobin (Hb) A2 values in the beta-thalassaemia carriers and accounted for 29%, 30% and 24% of their respective variances. beta-thalassaemia subjects with heterocellular HPFH had higher MCV and MCH values, concomitant with lower levels of Hb A2, and a reduced ineffective erythropoiesis. We conclude that co-inheritance of heterocellular HPFH leads to a primary increase in gamma-chain synthesis in beta-thalassaemia trait and can be another confounding factor in the use of red cell indices and Hb A2 levels in population screening for beta-thalassaemia.

In vivo metabolic studies of glucose, ATP and 2,3-DPG in beta-thalassaemia intermedia, heterozygous beta-thalassaemic and normal erythrocytes: 13C and 31P MRS studies

13C and 31P magnetic resonance spectroscopy was used to characterize the in vivo kinetics of glucose metabolism and intracellular ATP and 2,3-DPG concentrations in erythrocytes obtained from beta-thalassaemia intermedia, heterozygous beta-thalassaemic and normal individuals and maintained in suspension. Except for an upfield chemical shift in the 2P and 3P resonance of 2,3-DPG in the thalassaemia intermedia erythrocytes, the 31P spectra were comparable between all three blood types, showing similar concentrations of ATP (from 4.5 to 5.2 mumol/g Hb) and 2,3-DPG (from 17.2 to 19.7 mumol/g Hb). However, the profile of glucose metabolism was quite different in beta-thalassaemia intermedia erythrocytes, whereas glucose was consumed at a rate of 0.089 +/- 0.035 fmol/cell/h, significantly higher than that of normal (0.032 +/- 0.018 fmol/cell/h; P = 0.01) and heterozygous (0.025 +/- 0.004 fmol/cell/h; P = 0.01) erythrocytes. This near 3-fold faster rate of glucose metabolism in the thalassaemia intermedia erythrocytes could not be accounted for by any increase in glucose flux via the Embden-Meyerhof pathway, since no significant difference in 3-13C-lactate synthesis was observed among the three blood types (in units of fmol/cell/h, normal, 0.021 +/- 0.013; heterozygous, 0.021 +/- 0.006; beta-thalassaemia intermedia 0.045 +/- 0.025). These results reflect an accelerated rate of glucose metabolism in thalassaemia intermedia erythrocytes because the contribution of reticulocytes to this altered pattern of metabolism could be excluded. As the only other route of glucose metabolism in erythrocytes is the pentose phosphate pathway (PPP), these results indicate that the PPP is more active in beta-thalassaemia intermedia erythrocytes, perhaps as a consequence of their elevated intracellular oxidative state.

Reticulocyte counting in thalassemic and other conditions with the R-1000 Sysmex analyzer

Precise reticulocyte counts are difficult to obtain by the manual method when their percentage in the blood is low or normal. In these instances, rapid reticulocyte counting by flow cytometry appears to offer more accuracy and precision. The purpose of this study was to establish reticulocyte counts in heterozygous beta-thalassemia for reference purposes and to evaluate the performance of the recently introduced apparatus R-1000 (Sysmex) in the very heterogeneous thalassemic and sickle-cell syndromes. We studied a total of 364 samples; 102 heterozygous beta-thalassemia carriers, 180 normal matched controls, 36 patients with thalassemia major or intermedia, and 46 patients with various sickle-cell syndromes. Reticulocyte counts (both as percentage and as total number) were higher in heterozygous beta-thalassemia than in normal controls (p less than 0.001) and showed an inverse correlation with the respective hemoglobin values (p less than 0.001). These results confirm the proposed slightly increased erythropoietic activity in heterozygous beta-thalassemia carriers. A drawback of the technique is that the reticulocyte-platelet discrimination error is signaled frequently in all conditions displaying a marked red cell heterogeneity, especially when these are associated with high reticulocyte numbers. This calls probably for readjustment of the corresponding algorithm. In addition, all these conditions show a significantly increased auramine-O mature red-cell nonspecific fluorescence.

Folic acid deficiency in beta-thalassaemia heterozygotes

Plasma and red cell folate mean contents have been found to be significantly lower in 41 symptom-free beta-thalassaemia heterozygotes than in 21 controls. Such decreases must be considered as effects of an increased folate utilization caused by the enhanced total, both effective and ineffective, erythropoiesis. Since no close correlation has been found between packed cell volume and plasma or red blood cell folate levels, it seems that in 'healthy' beta-thalassaemia subjects, the degree of anaemia is not influenced by folate body reserves. However, the frequent finding of reduced red cell folate contents suggests that further folate imbalance might lead to clinically significant degrees of folate deficiency.

Haematological parameters in the healthy adult Egyptian population

Haemoglobin parameters, serum iron and the levels of haemoglobins A2 and F were examined in normal unrelated adult Egyptians (60 males and 142 females). The mean red cell volume and the mean red cell haemoglobin are low. Haemoglobin A2 in Egyptian adult males is slightly less than that in females.

The laboratory evaluation of microcytic red blood cells

Microcytic red blood cell states are common clinical problems in both adult and pediatric age groups. The recent widespread availability of electronic blood cell counters for performing routine blood counts has increased the detection of microcytic red blood cells. Physicians must workup both symptomatic and asymptomatic patients with microcytic red blood cells before they can initiate proper therapy and/or counseling. The purpose of this review is threefold: (1) to discuss the causes of microcytic red blood cells in terms of disorders of decreased heme production vs. disorders of decreased globin production, (2) to review the clinical laboratory tests useful in differentiating microcytic red blood cell states, and (3) to present a practical approach for the laboratory workup of microcytic red blood cells.

Genetic and biochemical heterogeneity of beta-thalassaemia in Naples

We have investigated 32 children with Cooley's anaemia from Naples, Italy. Criteria for inclusion in the study were: (a) typical clinical and haematological findings; (b) absolute transfusion requirement; and (c) elevated Hb A2 in both parents. From biosynthetic studies we have established that five children (including two sets of sibs) had beta-0 thalassaemia, while the rest had beta + thalassaemia. Thus, the frequency of beta + thalassaemia among unrelated patients was about 90%. The distribution of beta/alpha ratios among beta + patients ranged from 0.01 to 0.16 and it was bimodal, consistent with some of them having a beta-0/beta + genotype and others a beta +/beta + genotype. The distribution of beta/alpha ratios of the patients' parents (obligate heterozygotes) ranged from 0.24 to 0.73, and it was plurimodal, consistent with the coexistence in this population of multiple beta thalassaemia alleles, of which one must be beta-0 and at least one is beta +. A systematic analysis of 20 families indicates that the beta/alpha ratio is to some extent quantitatively inherited, and its suggests non-randomness in the assortment of beta thalassaemia alleles that can give rise to a Cooley's phenotype.

Quantitative evaluation of the mechanisms of the anaemia in heterozygous beta-thalassaemia

Ferrokinetic studies were carried out in 8 patients with heterozygous beta-thalassaemia with anaemia of varying severity. Effective and ineffective erythropoiesis, mean red cell lifespan and non-erythroid iron turnover were estimated from the experimental data through a mathematical model of iron kinetics. Erythropoietic activity was markedly increased in all patients, but was variably ineffective (from 10 to 74%). A negative correlation (r = 0.855, P less than 0.01) was found between the amount of ineffective erythropoiesis and Hb level. Red cell lifespan was variably shortened and there was a negative correlation between the degree of daily peripheral haemolysis and Hb level (r = 0.733, P less than 0.05). Non-erythroid iron turnover was increased in most patients. The results provide quantitative measurements of the mechanisms responsible for the wide variation of the Hb level in heterozygous beta-thalaeeaemia. Ineffective erythropoiesis seems to be the major reason for the anaemia. Peripheral haemolysis contributes to it, especially in the most severely affected patients. The increased non-erythroid iron turnover may be responsible for the pathology which characterizes heterozygotes in the adult life.

The importance of the genetic picture and globin synthesis in determining the clinical and haematological features of thalassaemia intermedia

Twelve carriers of thalassaemia intermedia were studied. Their clinical and haematological picture was distinctly different from that in both heterozygotes and homozygotes for beta thalassaemia. Several genetic patterns were found responsible for thalassaemia intermedia: beta/delta beta thalassaemia, alpha 2 beta/beta thalassaemia-heterocellular HPFH. In a few subjects the genetic picture indicated that the patients were homozygous for beta thalassaemia, in spite of the mildness of the clinical situation. The lack of genetic uniformity was refelcted in very wide Hb A2 (2.5--8.7%) and Hb F (7.5--96.9%) ranges, as opposed to the noticeable degree of biochemical uniformity indicated by the very similar imbalance of globin chain synthesis: 0.33-0.54 for the non-alpha/alpha chain ratio in the peripheral blood. The mean for this parameter (0.43 +/- 0.05) was significantly different (P less than 0.001) from that observed in heterozygous carriers (0.60 +/- 0.10) and homozygous carriers (0.11 +/- 0.05) for beta thalassaemia. The marrow blood displayed a comparable pattern. It is therefore suggested that the severity of thalassaemia is attributable to the degree of chain synthesis imbalance.

Thalassaemia types and their incidence in Sardinia

The frequency of thalassaemia syndromes in Sardinia was examined by a population survey. The data indicate that about 12.6% of the Sardinian subjects are carriers of beta-thalassaemia, while 6.9% of the population carries an alpha-thalassaemia gene, with a slight difference between the various provinces. These are among the highest frequencies of thalassaemia genes found in a Caucasian population today. A survey of hospital inpatients and outpatients showed a newborn incidence of homozygous beta-thalassaemia of 1 in 300. The reasons for the difference between the expected and observed incidence figures are discussed. Moreover, 3 subjects with deltabeta0-thalassaemia trait, 6 carriers of heterocellular persistence of fetal haemoglobin (HPFH), 1 sickle cell trait, and 3 subjects with Hb J Sardegna were found. Genetic heterogeneity of beta-thalassaemia syndromes in this population may generally result from interaction of alpha- and beta-thalassaemia genes.

Comparison of haematological features of the beta0 and beta+ thalassaemia traits in Jamaican Negroes

Haematological characteristics have been compared in 29 subjects with heterozygous beta0 thalassaemia and in 33 subjects with heterozygous beta+ thalassaemia, identified by the type of sickle cell-beta thalassaemia among close relatives, in a Jamaican Negro population. Total haemoglobin, MCV and MCH were significantly lower in the beta0 type but the level of Hb A2 was not significantly different. Individual values for MCV, MCH and Hb A2 in the beta+ type occasionally overlapped those in the normal population casting doubt on the adequacy of these criteria in identifying all cases of heterozygous beta+ thalassaemia. The haematological differences are those which would be expected on theoretical grounds. The inability to confidently differentiate the two types of heterozygous beta thalassaemia has implications for genetic counselling. The inability to distinguish heterozygous beta+ thalassaemia from normals on any single haematological index suggests that surveys depending on estimations of Hb A2 or on MCV alone may have underestimated the prevalence of the beta+ thalassaemia gene.