Homozygous Beta-thalassemia Patients Research Articles

Genotype-phenotype correlation among beta-thalassemia and beta-thalassemia/HbE disease in Thai children: predictable clinical spectrum using genotypic analysis.

IntroductionBeta-thalassemia is a group of inherited hemolytic anemias and one of the most common genetic disorders in Thailand. The clinical spectrum of beta-thalassemia disease ranges from mild to severe clinical symptoms including mild beta-thalassemia intermedia (TI) and severe beta-thalassemia major (TM).ObjectiveThis study aimed to determine the correlation between beta-globin gene (HBB) mutations and their phenotypic manifestations by evaluating patients’ clinical characteristics, transfusion requirements, growth and hematologic parameters, and hemoglobin typing among pediatric patients treated at Phramongkutklao Hospital.Materials and methodsSeventy beta-thalassemia patients, including 63 with beta-thalassemia/hemoglobin E (HbE) and 7 with either homozygous or compound heterozygous beta-thalassemia, were enrolled in this study. Their clinical presentation, growth parameters and laboratory findings were reviewed and analyzed. The mean follow-up time was 10.52±5.62 years. Mutation analysis in each individual was performed using multiplex amplification refractory mutation system (M-ARMS), direct DNA sequencing of beta-globin gene and gap PCR for 3.4 kb deletion detection.ResultsAll 7 homozygous and compound heterozygous beta-thalassemia patients were classified in TM. Among 63 patients with beta-thalassemia/HbE, 58 were classified in TM and 4 were classified in TI. Mean age at diagnosis was 0.8±0.49 years for homozygous or compound heterozygous beta-thalassemia and 3.43±3.5 years for beta-thalassemia/HbE. The most common HBB mutation was HBB:c.126_129delCTTT [codon 41/42 (-TCTT)] found in 34 alleles (48.6%). The height for age was also lower in homozygous beta-thalassemia patients (<3rd percentile) compared to compound heterozygous beta-thalassemia patients (25–50th percentile).ConclusionThis study revealed a genotype–phenotype correlation of the most prevalent beta-thalassemia in Thai children using diagnostic capacity in genotypic analysis of HBB mutation. Our findings can provide a better prediction of clinical manifestation and severity by early identification of the type of the HBB mutations.

Severe infections in thalassaemic patients: prevalence and predisposing factors

The incidence of infections among patients with thalassaemia and the role of risk factors for infection are uncertain. We studied the occurrence of infections necessitating hospitalisation in 92 homozygous beta-thalassaemia patients who had been followed longitudinally for decades, and investigated the role of potential risk factors for these infections. Pneumonia accounted for 26% of the infections and fever of unknown origin for 14%. Staphylococcus aureus was the major pathogen possibly related to injections associated with intensive chelation with deferoxamine. There was a significant increase in the rate of infection over time, notably after 15 years. Splenectomy correlated with the incidence of infection (P < 0.001) without being confounded by other variables and with highest frequencies of infections present after 10 years. A direct correlation between iron overload and infection was evident only before the initiation of iron-chelating treatment (P < 0.01). Following initiation of deferoxamine, paradoxically, the infection rate increased (P = 0.046). The combination of splenectomy and deferoxamine treatment was associated with the highest adjusted infection rate. Parathyroid dysfunction and glucose-6-phosphate dehydrogenase deficiency were significantly associated with infection (P = 0.02 and P = 0.04 respectively). The infection rate in thalassaemia is affected mainly by the duration of the disease and is increased by splenectomy and, in the long term, by treatment with deferoxamine.

Factors associated with the attitudes and expectations of patients suffering from beta-thalassaemia: a cross-sectional study.

Regular transfusions and iron chelation therapy have transformed the life expectancy of homozygous beta-thalassaemia patients, so that it can now be considered a chronic condition. A health questionnaire survey of all adults suffering from beta-thalassaemia major receiving treatment on the Island of Crete, Greece was carried out with the aim of ascertaining the factors that are associated with their attitudes and expectations. The responses of 67 of the 72 patients, aged 18-45 years, were analyzed using Principal Component Analysis to extract three component indicators (Adaptability, Optimism and Pessimism Indicators), which reflected their attitudes towards life and two component indicators (Healing and Therapy Indicators) that reflected their expectations from life. These were then tested against the respondents' socio-demographic characteristics, their health status and satisfaction with the services. It was found that the Optimism Indicator was associated with a positive comparative assessment of health status, while the Adaptability Indicator was associated with a positive subjective assessment of health status. The Adaptability Indicator was also higher in those satisfied with the services but it was lower in the best-educated group. The pessimism indicator was associated with a negative comparative assessment of health status and with the lowest level education. The expectation indicators showed an interaction with gender and other parameters such as admission to hospital. The relationship between the attitudes and the expectations of patients suffering from a chronically disability condition and specific experiences during their treatment regimens raises several issues related to the need for better health education and psychological support of the group of patients, as well as issues related to the communication skills of the staff caring for them.

Association of gingival crevicular fluid and serum intracytoplasmic enzyme levels in periodontally healthy homozygous (major) beta-thalassemia patients.

To assess tissue necrosis in beta-thalassemia major patients, as in other areas of medicine, lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) have been widely used. These markers of tissue degradation have also been studied in the gingival crevicular fluid (GCF) in relation to periodontal disease status. The purpose of this study was to investigate whether periodontal diagnostic tests based on these markers of tissue degradation are influenced from the enzymes' levels in serum and, therefore, could be used in the assessment of the patient's periodontal status. Forty-four periodontally healthy, homozygous beta-thalassemia patients were enrolled in the study. GCF and serum samples were obtained and the levels of AST, ALT and LDH were determined; the measurements took place in an automated analyzer (Hitachi 777) using the kits of Roche Company. Lack of correlations between serum and GCF enzyme levels was demonstrated. Serum LDH and serum AST, serum AST and serum ALT are significantly positively correlated. Concerning the GCF, AST and ALT were proved to be significantly positively correlated. Elevated values of LDH, ALT and AST in serum do not constitute a confounding factor in GCF measurements of the respective enzymes.

Rapid detection of beta-globin gene mutations and polymorphisms by temporal temperature gradient gel electrophoresis.

Inherited hemoglobin disorders represent the most common Mendelian disease worldwide. Prevention programs based on molecular diagnosis of heterozygous carriers and/or patients require the use of reliable mutation scanning methods in at-risk populations. We developed a rapid and highly specific mutation-screening test based on temporal temperature gradient gel electrophoresis (TTGE). We analyzed 889 beta-thalassemia genes from homozygous beta-thalassemia patients and unrelated individuals with heterozygous beta-thalassemia. Previously reported common mutations were screened by reverse dot blots using allele-specific probes. The rare mutations were analyzed by TTGE. We found common mutations in 753 beta-thalassemia genes. TTGE analysis in the rest of the genes showed the presence of mutations in different regions of the beta-globin gene in 134 of them, and these mutations were characterized by DNA sequencing. In the two genes in which mutations were not identified, large deletions spanning beta-globin gene were suspected. Compared with other approaches for comprehensive mutation screening, the reported method is rapid, highly sensitive, cost-effective, and suitable for high-throughput screening of a large number of samples.

Reproductive health in patients with beta-thalassemia.

Homozygous transfusion-dependent beta-thalassemia patients manifest cardiac, hepatic, endocrine, and metabolic disorders attributable to chronic anoxia and iron overload. Short stature, delayed sexual maturation, diabetes mellitus, hypothyroidism, hypoparathyroidism, and metabolic bone disease can and should be diagnosed as early as possible so that the intervention can be fruitful. Primary or secondary amenorrhea is due primarily to pituitary gonadotrope hemosiderosis, as attested by pathology data and the demonstration in vivo of nonstimulable follicle-stimulating hormone and luteinizing hormone release and secretion after the exogenous administration of gonadotropin-releasing hormone or its agonistic analogs. Ovulation can be achieved with the use of exogenous gonadotropins provided that the ovary has no siderosis (as seen in neglected patients) or damage induced by drugs used for bone marrow transplantation. Once pregnancy is achieved, it should be considered high risk and be dealt with or cared for by an expert team to ensure a successful outcome.

Molecular characterization of homozygous (high HbA2) beta-thalassemia intermedia in Greece.

Homozygous beta-thalassemia is usually characterized by severe anemia requiring regular blood transfusion for survival. For homozygous patients with milder clinical manifestations and no dependence on transfusion therapy, the term thalassemia intermedia is usually applied. Genetic mechanisms that may ameliorate the clinical expression of homozygous beta-thalassemia include coinheritance of alpha-thalassemia, inheritance of mild beta-globin gene mutations, and increased gamma-globin chain production, which may partially compensate for the lack of beta-globin chain synthesis. To identify which of these factors may contribute to the modification of childhood homozygous, high-hemoglobin A2 (HbA2) beta-thalassemia in Greece, the interaction of alpha-thalassemia, types of beta-thalassemia mutations, and the presence of a polymorphic site 5' to the G gamma-globin gene, which has been described as associated with increased gamma-globin chain production in some cases, was assessed. The results were analyzed in light of similar studies in 150 randomly selected, homozygous, high-HbA2 beta-thalassemia patients with the aim of assessing whether thalassemia genotypes can provide information useful for prognosis and/or more appropriate management of homozygous beta-thalassemia patients. The results indicate that, in general, the major factor modifying the clinical expression of homozygous, high-HbA2 beta-thalassemia in Greece is the inheritance of mild beta-thalassemia mutations. Although there is not always a complete correlation of genotype with clinical phenotype, the inheritance of two mild beta-thalassemia alleles results in almost all cases (11 of 12 cases in this study) in thalassemia intermedia phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Polymorphic pattern of the (AT)X(T)Y motif at -530 5' to the beta-globin gene in over 40 patients homozygous for various beta-thalassemia mutations.

Nucleotide sequence analysis of the 5' beta-globin gene flanking region has been carried out for numerous homozygous beta-thalassemia patients with different mutations and of various ethnic backgrounds. Four different rearrangements were found associated with numerous beta-thalassemia mutations. The (AT)X(T)Y repeat motif at -530 showed polymorphic patterns among these patients as follows: All ten IVS-II-1 (G-->A) chromosomes and the two with the -87 (C-->G) mutation are associated with the (AT)9(T)5 rearrangement, while the 30 IVS-I-6 (T-->C), the 16 codon 39 (C-->T), the six codon 8 (-AA) chromosomes, and 12 chromosomes with different promoter mutations had the (AT)7(T)7 motif. Six chromosomes with the promoter mutation at position -29 (A-->G) had the (AT)8(T)6 motif, while an (AT)8(T)4 motif appears characteristic for two IVS-I-5 (G-->A and G-->T). No direct association between any of the (AT)X(T)Y arrangements and an increased gamma gene expression [G gamma and fetal hemoglobin (Hb F)] levels could be demonstrated, suggesting that variations in the (AT)X(T)Y motif are common polymorphisms.

Genetic epidemiology of beta-thalassemia in Sicily: do sequences 5' to the G gamma gene and 5' to the beta gene interact to enhance HbF expression in beta-thalassemia?

The present epidemiological study of the molecular characteristics of beta-thalassemia in Sicily was prompted by the disparate phenotypic expression (in clinical status and absolute HbF level) observed in two beta-thalassemic homozygotes who were also homozygous for the beta-like globin gene cluster haplotype III. We suspected that polymorphisms within haplotype III could be the cause for the discrepancy. Based on the association of particular conformations of the (AT)xT(y) motif (-540 5' to the beta gene) with milder forms of thalassemia and sickle cell anemia, 38 homozygous beta-thalassemia patients were studied to define their haplotypes, the -158 site 5' to the G gamma gene (linked to haplotype III) and the structure of the (AT)xT(y) motif. We found that the patient who was phenotypically mild and homozygous for beta-thalassemia, haplotype III, and the -158 C----T mutation was homozygous for the rare (AT)9T5 motif. In contrast, the patient homozygous for beta-thalassemia, haplotype III, and the -158 mutation, but exhibiting a severe clinical course, was homozygous for the (AT)7T7 configuration. Others have suggested that (AT)9T5 is a negative regulatory protein binding sequence, and it is a silent carrier state for beta-thalassemia. The usual configuration (AT)7T7, has considerably less affinity for regulatory protein binding, and it is the most common configuration in Sicilian beta-thalassemics (67 of the 78 chromosomes studied). Within the 38 patients studied, seven were informative because they had various combinations of the (AT)9T5 and (AT)7T7 motif, and the -158 C----T mutation. The results in these patients suggest that only the co-presence of the (AT)9T5 configuration and a C----T change at -158 5' to the G gamma gene is associated with high HbF expression and a mild clinical phenotype. We postulate that these two regions of the beta-like globin gene cluster interact, when endowed with the proper sequences, to enhance the expression of HbF secondary to anemia.

Vitamin B12, folate, and iron studies in homozygous beta thalassemia.

The efficacy of serum folate (SF), red blood cell folate (RCF), and serum B12 in diagnosing folate and B12 deficiency, and the effect of iron overload on hemoglobin, were studied in 157 cases of homozygous beta thalassemia (HBT). The patients had lower SF compared with normal subjects (NS) (P less than 0.001) and higher RCF than their parents (P less than 0.001) and NS (P less than 0.001). Forty percent of patients had both low SF (less than 3 ng/mL) and high RCF (greater than 600 ng/mL). Homozygous beta thalassemia patients are known to have folate deficiency. Yet, both folate and B12 deficiency status were similar in the authors' patients and NS. These deficiencies apparently were less in patients compared with their parents, who shared the same nutritional milieu (P less than 0.001). Mean hemoglobin in patients with iron overload (transferrin saturation, TS greater than 50%) was lower than in those without (P less than 0.005). The following is concluded: (1) diagnosis of folate and B12 deficiency based on SF, RCF and serum B12 is vitiated in HBT and needs a therapeutic trial; (2) iron overload of a magnitude indicated by TS greater than 50% can aggravate anemia in HBT.

Influence de la transfusion sanguine sur l'erythropoïèse des patients bêta thalassémiques homozygotes

The influence of blood transfusion on erythropoiesis (bone marrow erythroblasts, peripheral blood erythroblasts and reticulocytes) has been studied in 20 non splenectomized homozygous beta thalassaemia patients aged 3 to 16 years and in 10 splenectomized patients aged 8 to 24 years affected with the same disease. The number of reticulocytes was the same in the two groups but the number of erythroblasts in the splenectomized group was higher than in the other group. There was no correlation between the erythroblasts and the reticulocytes of the peripheral blood on one hand and the haemoglobin level proceeding from the same sample on the other hand. In the non splenectomized group of patients, an inverse relationship was found between the percentage of bone marrow erythroblasts and the mean annual haemoglobin level (r = -0.71; p less than 0.01). These results demonstrate the effect of blood transfusion on the erythroid cell line in homozygous beta thalassaemia and the delay between the transfusions and the medullary erythroblastic response.

Common haplotype dependency of high G gamma-globin gene expression and high Hb F levels in beta-thalassemia and sickle cell anemia patients.

We have studied 42 homozygous beta-thalassemia patients from Algeria and 34 sickle cell anemia patients from Senegal and Benin, determining the relationship between haplotypes, Hb F, and G gamma-globin/A gamma-globin ratios. Populations selected have a high frequency of haplotype homozygotes because of consanguinity (Algeria) and geographic homogeneity (West Africa). We find in beta-thalassemia patients, that haplotype IX in haplotypic homozygotes and heterozygotes, haplotype III in heterozygotes, and the Senegal haplotype in sickle cell anemia patients are all linked to high G gamma-globin expression. In addition, haplotypes IX and Senegal, but not haplotype III, have high Hb F levels. All of these haplotype have a common subhaplotype (+- ) in the gamma-globin gene region. In addition, haplotypes IX, III, and Senegalese sickle cell anemia patients exhibit hematological amelioration of their disease. Conversely, haplotypes I, V, and A in thalassemia patients, which also have a common subhaplotype (-----), and the Benin subhaplotype (--++-) in sickle cell anemia patients are all associated with low G gamma-globin and low Hb F levels. Low G gamma-globin expression in the adult is associated with two haplotypes that are not common between thalassemia and sickle cell anemia patients. We conclude that the determinant for high G gamma-globin expression is haplotype-linked to common and genetically dominant subhaplotypes in the two diseases. The total Hb F level, unlike the high G gamma-globin expression, however, is linked to haplotypes but not to subhaplotypes, thus dissociating the two genetic effects.

Globin Synthetic Ratios in Homozygous β-Thalassemia Patients from Lebanon

We have studied patients with beta-thalassemia from a Lebanese population having a high rate of consanguineous matings. This population exhibits both elevated and normal levels of Hb A2 associated with high levels of Hb F in homozygotes. The clinical course of the anemia suggests that this population consists of the severe Mediterranean type. Twenty-three unrelated homozygous beta-thalassemia patients investigated for globin synthetic ratios, consisted of 18 beta+ and 5 beta 0 with a non-alpha/alpha range of 0.158-0.465 and 0.25-0.41, respectively. The percentage of G gamma chains in Hb F was determined for 21 of these patients and a mean value of 59% G gamma chain content was found.