ITPA Polymorphisms and the Incidence of Toxicities in Children with Acute Lymphoblastic Leukemia.

Background: 6-Mercaptopurine (6-MP), a thiopurine agent, is a essential medication for treating pediatric acute lymphoblastic leukemia (ALL). However, its side effects of neutropenia and hepatotoxicity might interrupt treatment, resulting in poor outcomes. Inosine triphosphate pyrophosphatase (ITPA), an enzyme in the thiopurine pathway, may prevent the accumulation of toxic thiopurine metabolites. Studies on ITPA and thiopurine-associated toxicities are scarce. Methods: This study retrospectively investigated 1- to 15-year-old children with ALL who received 6-MP during the maintenance phase of treatment between 2000 and 2020. Toxicity during the first year of maintenance therapy and the mean dose of 6-MP were analyzed. Results: The 209 patients had a median age of 4.8 (0.3-14.8) years. Of these, 124 patients (59.3%) had wild-type ITPA, 73 patients (34.9%) had heterozygous ITPA 94C>A (hetITPA), and 12 patients (5.7%) had homozygous ITPA 94C>A (homITPA), with an allele frequency of 0.23. The incidence of neutropenia among ITPA polymorphisms did not significantly differ (P = 0.813). In patients harboring homITPA, transaminitis was more frequent than other polymorphisms but without a significant difference (P = 0.063). The mean dose of 6-MP for patients with homITPA was significantly lower than that for patients with hetITPA or wild-type ITPA (P = 0.016). Conclusions: HomITPA had a higher incidence of transaminitis and required a significantly larger dose reduction of 6-MP than wild-type ITPA. Further study is warranted to elucidate the effects of ITPA polymorphisms on toxicity in patients with ALL treated with 6-MP.

Mutations in Kruppel-like factor 1 cause transfusion-dependent hemolytic anemia and persistence of embryonic globin gene expression.

In this study, we report on 8 compound heterozygotes for mutations in the key erythroid transcription factor Krüppel-like factor 1 in patients who presented with severe, transfusion-dependent hemolytic anemia. In most cases, the red cells were hypochromic and microcytic, consistent with abnormalities in hemoglobin synthesis. In addition, in many cases, the red cells resembled those seen in patients with membrane defects or enzymopathies, known as chronic nonspherocytic hemolytic anemia (CNSHA). Analysis of RNA and protein in primary erythroid cells from these individuals provided evidence of abnormal globin synthesis, with persistent expression of fetal hemoglobin and, most remarkably, expression of large quantities of embryonic globins in postnatal life. The red cell membranes were abnormal, most notably expressing reduced amounts of CD44 and, consequently, manifesting the rare In(Lu) blood group. Finally, all tested patients showed abnormally low levels of the red cell enzyme pyruvate kinase, a known cause of CNSHA. These patients define a new type of severe, transfusion-dependent CNSHA caused by mutations in a trans-acting factor (Krüppel-like factor 1) and reveal an important pathway regulating embryonic globin gene expression in adult humans.

Clinical presentation and molecular identification of four uncommon alpha globin variants in Thailand. Initiation codon mutation of α2-globin Gene (HBA2:c.1delA), donor splice site mutation of α1-globin gene (IVSI-1, HBA1:c.95 + 1G>A), hemoglobin Queens Park/Chao Pra Ya (HBA1:c.98T>A) and hemoglobin Westmead (HBA2:c.369C>G).

Alpha thalassemia is the most common genetic disease in the world with the prevalence of carriers ranging from 5-50% in several populations. Coinheritance of two defective α-globin genes usually gives rise to a symptomatic condition, hemoglobin (Hb) H disease. Previously, it has been suggested from several studies in different populations that nondeletional Hb H disease (--/α(T)α or --/αα(T)) is generally more severe than the deletional type (--/-α). In this report, we describe four rare nondeletional α-thalassemia mutations in Thai individuals, including initiation codon mutation (HBA2:c.1delA), donor splice site mutation (IVSI-1, HBA1:c.95 + 1G>A), Hb Queens Park (HBA1:c.98T>A) [α32(B13)Met>Lys], and Hb Westmead (HBA2:c.369C>G) [α122(H5)His>Gln]. Interactions of the first three mutations with the α(0)-thalassemia resulted in nondeletional Hb H disease; however, their clinical presentations were rather mild and some were detected accidentally. This suggests that a genotype-phenotype correlation of α-thalassemia syndrome might be more heterogeneous and so the type of mutation does not simply imply the prediction of the resulting phenotype. Our data will be of use in future genetic counseling of such conditions that are increasingly identified thanks to the improvement of molecular analysis in routine laboratories.

Association of xmn I polymorphism and hemoglobin e haplotypes on postnatal gamma globin gene expression in homozygous hemoglobin e.

Background and Objectives. To explore the role of cis-regulatory sequences within the ß globin gene cluster at chromosome 11 on human γ globin gene expression related to Hb E allele, we analyze baseline hematological data and Hb F values together with ß globin haplotypes in homozygous Hb E. Patients and Methods. 80 individuals with molecularly confirmed homozygous Hb E were analyzed for the ß globin haplotypes and Xmn I polymorphism using PCR-RFLPs. 74 individuals with complete laboratory data were further studied for association analyses. Results. Eight different ß globin haplotypes were found linked to Hb E alleles; three major haplotypes were (a) (III), (b) (V), and (c) (IV) accounting for 94% of Hb E chromosomes. A new haplotype (Th-1) was identified and most likely converted from the major ones. The majority of individuals had Hb F < 5%; only 10.8% of homozygous Hb E had high Hb F (average 10.5%, range 5.8-14.3%). No association was found on a specific haplotype or Xmn I in these individuals with high Hb F, measured by alkaline denaturation. Conclusion. The cis-regulation of γ globin gene expression might not be apparent under a milder condition with lesser globin imbalance such as homozygous Hb E.

Rapid flow cytometric test using eosin-5-maleimide for diagnosis of red blood cell membrane disorders.

Conventional diagnosis of hereditary red blood cell (RBC) membrane disorders, in particular hereditary spherocytosis (HS), is labor intensive, time consuming and requires at least 2 ml of blood, which might be impractical in neonatal period. We evaluated the use of eosin-5-maleimide (EMA), a dye that reacts covalently with lysine-430 on the first extracellular loop of band 3 protein, for rapid screening test of patients with HS and Southeast Asian Ovalocytosis (SAO). Fresh RBCs from 142 healthy controls, 50 HS, 17 SAO, 29 hereditary elliptocytosis, 5 autoimmune hemolytic anemia, 66 patients with beta-thalassemia/HbE, 31 cases with alpha-thalassemia (HbH disease) and 4 cases with pyruvate kinase deficiency were stained with EMA, and analyzed for their mean channel fluorescence (MCF) using a flow cytometer. RBCs from patients with HS and SAO expressed a greater degree of reduction in MCF compared to those from normal controls and other hemolytic diseases. These findings showed that the fluorescence flow cytometric-based method is a simple, sensitive and reliable diagnostic test for RBC membrane disorders using a small volume of blood, and results could be obtained within 2 hours. Such method could serve as a first line screening for the diagnosis of HS and SAO in routine hematology before further specific membrane protein electrophoresis and molecular diagnosis are employed.

Clinical and hematological phenotype of homozygous hemoglobin E: revisit of a benign condition with hidden reproductive risk.

Hemoglobin E (HbE) is one of the most prevalent beta-globin variant, which is widely distributed in Southeast Asia especially in Thailand. Homozygosity for this variant is common and may occur with iron deficiency. In order to study clinical and hematological phenotypes without the confounding effect of iron deficiency, investigations were carried out before and after iron supplementation for 2 months. The effect of G6PD deficiency and coinheritance of alpha-thalassemia in homozygous HbE were also studied. HbE homozygotes were clinically benign, never had been transfused and had no hepatosplenomegaly. Out of 76 HbE homozygotes, hematological parameters of 7 individuals with iron deficiency improved after iron supplementation. Hemoglobin analysis revealed that HbE was the main hemoglobin detected, but 12 subjects were found to have a substantial percentage of HbF, which might lead to misdiagnosis as HbE/beta-thalassemia. Both clinical and hematological phenotypes of simple homozygous HbE did not differ from those who also inherited alpha-thalassemia and/or G6PD deficiency. It is necessary to perform a comprehensive DNA analysis for alpha-thalassemia in cases of homozygous HbE when their partner is suspected of having alpha-thalassemia 1 gene.

Development of a comprehensive red blood cell enzymopathy laboratory in Thailand: the study of normal activity in eight erythroenzymes in Thais.

In order to provide a reference range for normal red blood cell enzyme activities in Thai, we analyzed data from 113 healthy non-anemic Thai people (55 males and 58 females) age 1-42 years, who all had a normal pattern of hemoglobin typing (HbA and HbA2 less than 3.5%). Hematological analysis was performed using an automated cell counter and the hemoglobin studies were carried out by low pressure liquid chromatography. Owing to a high frequency of alpha-thalassemia in Thailand, cases with an MCV < 75 fl were excluded from the study since these cases were likely to be heterozygotes for alpha0-thalassemia. Cases with reticulocytes > 2.5% were excluded from the study since reticulocytes have a higher enzyme activity than mature erythrocytes. Cases with abnormal red blood cell morphology, such as spherocytes and ovalocytes, were also excluded. These criteria were applied to select "normal" controls for our analysis. We assayed eight red blood cell enzyme activities in normal subjects: glucose-6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogenase (6PGD), pyruvate kinase (PK), hexokinase (HK), glucose phosphate isomerase (GPI), phosphofructokinase (PFK), aldolase (ALD) and phosphoglycerate kinase (PGK). The mean normal ranges (+/- SD) for G6PD, 6PGD, PK, HK, GPI, PFK, ALD and PGK were 12.7 (+/-2.2), 10.7 (+/-1.3), 18.5 (+/-4.0), 1.5 (+/-0.4), 80.5 (+/-11.8), 11.8 (+/-2.1), 4.5 (+/-1.6) and 370 (+/-43) IU/gHb, respectively. Age-dependent differences for the reference values for these enzyme activities were summarized. All red blood cell enzyme activities were highest during the early childhood period and slightly lower in the adult period. These values will be of clinically useful for future reference.

Flow cytometric quantitation of opsonophagocytosis and intracellular killing of Candida albicans using a whole blood microassay.

Flow cytometric assays for quantifying polymorphonuclear leucocyte (PMN) function involve peripheral blood fractionation methods. However, most are of limited use for conditions like pediatrics and thalassemia, as they may require large blood volumes or complicated by red blood cell contamination. In whole blood assay, 500-mul aliquots of normal or thalassemic whole blood were incubated with bis-carboxyethyl-carboxyfluorescein pentaacetoxymethylester (BCECF-AM)-labeled Candida albicans cells and phycoerythrin-conjugated anti-CD13 monoclonal antibody for PMNs. Phagocytosis was quantitated by gating on CD13 label PMNs and determining the frequency of phagocytosed yeast using flow cytometry. The killing activity was quantitated by estimating the number of viable fluorescence retaining yeast cells liberated following lysis of PMNs. In normal control or thalassemia samples, nonphagocytosed yeast and PMNs with or without phagocytosed yeast were readily distinguished by two-color dot plot, permitting phagocytosis estimates. Viable and nonviable yeast killed by whole blood PMNs were distinguished by side scatter and fluorescence, permitting killing estimates. The patterns seen using whole blood was similar to that seen with fractionated PMNs. Data from thalassemia patients showed similar opsonophagocytosis but slightly decreased intracellular killing of yeast cells when compared with normal subjects. This assay provides an alternative method to assess PMN function in small blood samples, which could be especially useful in conditions like thalassemia and pediatric patients.

Prevalence of HFE mutations among the Thai population and correlation with iron loading in haemoglobin E disorder.

Co-inheritance of HFE mutations has a substantial role in iron overload in beta-thalassaemia carriers in north European populations where two HFE mutations, C282Y and H63D, are prevalent. In Thailand, there was little information about the allele frequency of HFE mutations. It is of interest to determine whether such determinants represent a potential risk in developing iron overload as nearly 40% of the Thai population carry either one of thalassaemia or haemoglobinpathy alleles. A total of 380 normal controls from five different regions including Bangkok were screened for the HFE C282Y, H63D and IVS5+1 G-->A alleles. In addition, 70 individuals with homozygous haemoglobin E (Hb EE) were also tested and their genotypes were correlated with levels of serum ferritin. H63D is the major HFE mutation found in the Thai population with an average allele frequency of 3% (range 1-5%). One individual was heterozygous for the splice site mutation IVS5 + 1 G --> A, and the C282Y allele was not detected. In the Hb EE group, five individuals had iron deficiency (ferritin <12 microg/L) and the remaining 65 individuals had a wide range of serum ferritin levels of 16-700 microg/L. Four individuals with Hb EE were heterozygous for the H63D allele. No significant difference in serum ferritin level was detected in this group with or without the HFE mutation (137.2 +/- 78 vs. 116.3 +/- 128 microg/L). HFE mutations are relatively uncommon among the Thai population, and the average allele frequency of the ancient H63D mutation is similar to that of other countries in this region. Because of their paucity, it appears that these alleles are less likely to be responsible for high ferritin levels and iron loading in individuals with Hb E related disorders.

Effect of red blood cell glucose-6-phosphate dehydrogenase deficiency on patients with dengue hemorrhagic fever.

Eighty nine males aged 1-13 years diagnosed with dengue haemorrhagic fever (DHF) and admitted to the Department of Pediatrics Siriraj Hospital from March 1998 to April 2000 were included in this study. 17 cases (19.1%) had red blood cell glucose-6-phosphate dehydrogenase (G-6-PD) deficiency and 72 cases (80.9%) had normal G-6-PD enzyme activities. Most of the patients were classified as DHF grade II in severity. 3 of 17 G-6-PD deficient cases had serious complications and all of them had acute intravascular hemolysis requiring blood transfusions. One of these also had hematemesis, one had azothemia and the other one had renal failure and severe liver failure with hepatic encephalopathy. In the cases without obvious hemolytic or hepatic complications, G-6-PD deficient cases had mildly but significantly higher total birirubin and indirect bilirubin, as well as a lower hematocrit than those who had normal G-6-PD. Reticulocyte count was low during the acute phase, however, during recovery, the levels were significantly increased in both groups. In the non G-6-PD deficient group, G-6-PD enzyme levels were significantly decreased during the acute phase compared to the normal controls but rose significantly to normal levels during the recovery phase. There were no statistically significant differences in other laboratory data. All patients recovered fully from DHF. The prevalence of G-6-PD deficiency in male patients who had DHF in this study was 19.1 per cent which was higher than the prevalence in a previous study of 12 per cent in Bangkok. This may imply that G-6-PD deficient males suffer more from DHF compared to normal G-6-PD subjects.

Allele related mutation specific-polymerase chain reaction for rapid diagnosis of Hb New York (beta 113 (G15) Val-->Glu, beta(CD113 GTG-->GAG)).

Hemoglobin New York (beta 113 (G15) Val-->Glu), a beta-globin variant, was first reported in a Chinese family living in New York. Subsequently, this abnormal hemoglobin was reported in many Chinese descendants from several groups and it was also known as Hb Kaohsiung. The subtle change in alpha1beta1 contact region apart from the heme group connecting area by Val-->Glu substitution has minor changes in both the electrophoretic mobility and stability making this hemoglobin variant difficult to distinguish from Hb A using routine hemoglobin analysis. The authors described a case of heterozygosity of Hb New York diagnosed by a molecular technique and revealed a mutation in beta(CD113 GTG-->GAG). A novel Allele Related Mutation Specific-Polymerase Chain Reaction (ARMS-PCR) for rapid diagnosis of this mutation has been proposed.