Erythrocyte glucose-6-phosphate dehydrogenase and pyruvate kinase activities in hemoglobin H disease

Erythrocyte glucose-6-phosphate dehydrogenase (G6PD) and pyruvate kinase (PK) activities were studied in hemoglobin H (HbH) patients by spectrophotometric method, cytochemical method and the methemoglobin reduction (MR) test for the detection of heterozygous G6PD deficiency. G6PD deficiency was found in 7 of 64 cases (10.9%), including 3 cases of genotype alpha 1/alpha 2 and 4 cases of genotype alpha 1/CS. None of the HbH patients was found to be PK-deficient. Spectrophotometrically determined G6PD and PK activities were significantly higher in HbH patients than in normals (p less than 0.001), whereas the MR test yielded a significantly lower percentage of residual methemoglobin in HbH patients than in normals (p less than 0.05). All three methods were efficient in the detection of hemizygous G6PD deficiency in HbH patients, but not in G6PD-deficient females.

Fetal red cell staining: method evaluation

Acid elution methods have been extensively used for the identification of fetal red cells in pregnant women with fetomaternal hemorrhage. A number of methods have been described: Kleihauer-Betke, Boehringer Mannheim, Fetaldex, Nierhaus-Betke modification and Sanguansermsri amido black B. A comparative evaluation of these methods was performed in this study. The technique of Sanguansermsri using amido black B was found to be more advantageous than the others in terms of simplicity, accuracy, precision and time taken.

Molecular heterogeneity of beta-thalassemia in Thailand

beta-Globin genes in 294 chromosomes of beta-thalassemia homozygotes and patients of beta-thalassemia/HbE in the northeast, the middle and the south of Thailand were analyzed by the PCR related techniques: dot blot hybridization, direct restriction assay, direct cloning and direct sequencing of the amplified DNA fragments. Twelve different mutations were detected at various frequencies. They are an A-G at-28, codon 19 (AAC-AGC), a G-T at IVS-1 nt1,a G-C at IVS-1 nt5, a C-T at IVS-2 nt654, a G addition in codons 8/9, a C deletion in codon 41, a 4 bp deletion in codons 41/42, an A addition in codons 71/72, an AAG-TAG in codon 17, a CAG-TAG in codon 26, a TAC-TAA in codon 35 and a 8 bp deletion in codons 123-125. We also developed allele specific-polymerase chain reaction to facilitate non-radioactive detection of the mutation. Origins and spread of mutations are speculated based on the results of determination of haplotypes and frameworks that are linked to the thalassemia alleles.

Hb Q-Thailand [alpha 74(EF3)Asp-->His]: gene organization, molecular structure, and DNA diagnosis

Hb Q-Thailand [alpha 74(EF3)Asp-->His] is often found in Thailand, China, and other Southeast Asian countries. The alpha-Q-Thailand gene is strongly linked to an alpha gene deletion and has important implications in the identification and diagnosis of hemoglobinopathies and thalassemias. The alpha-Q-Thailand mutation was previously mapped to the alpha 1 gene in a study of Chinese patients. In this paper, a Thai patient with Hb Q-Thailand/Hb H disease and his mother were studied at the DNA level, and the gene organization of Hb Q-Thailand in the Thai patient was found to be the same as that of Chinese patients (i.e. the Hb Q-Thailand gene is located on the alpha 1 gene of chromosome #16, while the -4.2 kb or leftward deletion involves the alpha 2 gene). Also, the GAC-->CAC mutation proposed at codon 74, has been confirmed by DNA sequencing and a simple and accurate method for diagnosis of the Hb Q-Thailand variant has been developed based on restriction enzyme analysis. Since the GAC-->CAC mutation generates new cutting sites for both restriction enzymes Apa LI and Hgi AI, polymerase chain reaction amplification of a specific region around codon 74, followed by digestion with these enzymes and agarose gel electrophoresis of the digested products, permits rapid and accurate identification of Hb Q-Thailand.

Erythrocyte volume and haemoglobin concentration in haemoglobin H disease: discrimination between the two genotypes

Erythrocyte volume and haemoglobin concentration in individual red cells from 62 patients with Hb H disease: 37 with H genotype (alpha-thalassaemia 1/alpha-thalassaemia 2) and 25 H/CS genotype (alpha-thalassaemia 1/Hb Constant Spring) were measured using the H*1 haematology analyser. All 25 cases with H/CS genotype, the more severe genotype, had microcytes (red cells with a volume smaller than 60 fl) less than 35% and hypochromic red cells (red cells with haemoglobin concentration less than 28 g/dl) more than 35%. A discriminant function, the ratio between the percentage of hypochromic red cells and the percentage of microcytes (Hypo/Micro), was proposed. Most of the H/CS patients (76%) had Hypo/Micro greater than 2.5 whereas those of H patients (82%) were below 2.5. Red cell volume histograms were also characteristically different between the two genotypes: the H/CS had a peak between 60 and 90 fl while the H genotype showed a peak at or very close to 60 fl, indicating a greater degree of microcytosis. Increased hypochromia with a slight decrease in cell size of H/CS red cells suggests that the poor degree of haemoglobinization has no linkage or very little role in disturbing the synthesis of membrane proteins and their assembly to the plasma membrane.

Erythroblast- and erythrocyte-bound antibodies in alpha and beta thalassaemia syndromes

Thirty-five Thai patients with various alpha-thalassaemia (alpha-thal 1/alpha-thal 2, alpha-thal 1/HbCS, HbCS/HbCS) and beta-thalassaemia (beta-thal/HbE, severe and mild form, HbE/HbE) syndromes were examined for the presence of immunoglobulins and C3d on o-tolidine positive erythroblasts in the bone marrow, and for the amounts of IgG of some specificities bound to circulating erythrocytes. In mild, but not in severe beta-thal/HbE and in alpha-thalassaemia, the percentages of Ig-positive erythroblasts were significantly higher than in controls and correlated well with the percentage of IgG-positive erythroblasts. By contrast, the percentages of IgM and C3d positive erythroblasts were low and similar in thalassaemic and control marrows. A substantial proportion of thalassaemic patients showed more erythrocyte-bound IgG than controls, but statistically significant elevations were seen only in severe beta-thal/HbE. Within a particular syndrome erythrocyte-bound IgG was more abundant in splenectomized than non-splenectomized subjects. It showed specificity for spectrin in some beta-thalassaemic patients and for band 3 protein in several individuals with alpha- or beta-thalassaemia. The results suggest that IgG antibodies play a role in the haemolysis of thalassaemia and that they are likely to be involved in the ineffective erythropoiesis in at least some of the syndromes studied.

Hemoglobin constant spring in Bangkok: molecular screening by selective enzymatic amplification of the alpha 2-globin gene

Hemoglobin Constant Spring (Hb CS) is a hemoglobin variant with an elongated alpha-globin chain secondary to a chain termination mutation. The diagnosis of HbCS by electrophoresis is difficult because it is present in very low amounts in the red cells of heterozygotes. Selective enzymatic amplification of the alpha 2-globin gene and allele-specific hybridization for Hb CS gene provided accurate diagnosis of Hb Constant Spring. We have used this approach to detect the alpha cs mutation in the cord blood that contained all four alpha-globin genes but had Hb Bart on electrophoresis. The alpha cs mutation was found in six subjects whose Hb Bart levels were 3.0, 3.2, 3.7, 4.0, 4.9, and 9.8%. The latter also had -alpha mutation on the other chromosome, giving rise to the genotype alpha cs alpha/-alpha, which produced high Hb Bart. The gene frequency for alpha cs in the Thai calculated from a total of 406 cord blood studied in Bangkok was found to be approximately 0.008.

Double heterozygosity of the beta-Malay and a novel beta-thalassemia gene in a Thai patient

The beta-globin genes from a Thai patient compound heterozygous for beta(+)- and beta zero-thalassemias were investigated. Amplification and DNA analysis of genomic DNA by the polymerase chain reaction procedure permitted the identification of the beta-Malay mutation (beta 19;AAC-AGC) in one allele and a novel beta zero-thalassemia mutation (41;TTC-TT) in another allele.

High-dose intravenous immunoglobulin in the management of immune hemolysis in patients with thalassemic disease: factors which determine refractoriness

We report our experience with high dose intravenous immunoglobulin (IVIg) in 3 thalassemic patients who had evidence of possible immune hemolysis. In 2 patients who had serious sepsis, their responses to IVIg were only partial and transient. The other patient who had marked splenomegaly had no evidence of response to IVIg. Both serious infections and large spleen may hamper the effect of IVIg and should be considered before IVIg is to be used in thalassemia.

Asymmetrically primed selective amplification/temperature shift fluorescence polymerase chain reaction to detect the hemoglobin Constant Spring mutation

Hemoglobin (Hb) Constant Spring is an alpha-thalassemic hemoglobinopathy that is a major cause of severe alpha-thalassemia in Southeast Asians. The difficulty of diagnosing Hb Constant Spring using standard electrophoretic methods has led to interest in DNA-dependent diagnostic methods. The methods developed have had to contend with the high degree of homology of the alpha 2-globin gene (the site of the Hb Constant Spring mutation) and the alpha 1-globin gene. We have developed a single reaction polymerase chain reaction-based method that uses asymmetric priming and a temperature shift to accomplish dual ends, selective amplification of alpha 2 but not alpha 1 DNA and discrimination of normal and Hb Constant Spring alpha 2 genes by allele-specific fluorescence polymerase chain reaction. Advantages of this method over previous approaches include avoiding radioisotopes, precluding the need for electrophoresis, and serving as its own control for successful amplification. It is readily applicable to routine diagnosis, population screening, and prenatal diagnosis.

Red cell and plasma calcium, copper and zinc in beta-thalassemia/hemoglobin E

Beta-thalassemia/Hb E is a genetic disease prevalent in Thailand. This study has used atomic absorption spectroscopy to evaluate red cell and plasma calcium, copper and zinc in patients with beta-thalassemia/Hb E, both splenectomized and non-splenectomized. The levels of these trace elements in both red cells and plasma were different between the non-thalassemic controls and the disease patients. The most prominent result was that calcium concentration in red cells increased significantly in thalassemia subjects, particularly in splenectomized cases. These results might reflect the abnormal trace element metabolism and defects in the calcium transport system of the red cell membrane in thalassemia.

Prenatal diagnosis of thalassemia and hemoglobinopathies in Thailand: experience from 100 pregnancies

In this review, we describe a simple strategy to detect the three severe thalassemic diseases commonly found in Thailand. Hb Bart's hydrops fetalis can be detected unambiguously by ultrasonography at 18-20 weeks of gestation or detected early in the first trimester by the gene amplification technique. Prenatal diagnosis for homozygous beta-thalassemia is better performed in the second trimester by in vitro protein synthesis. This is because the molecular defects of some beta-thalassemias are still unknown and homozygosity of the same mutation is low. In contrast, beta-thalassemia/Hb E is easily detected, in the first trimester, by direct visualization on electrophoresis or by dot blot analysis of enzymatically amplified DNA with a set of nonradioactively labeled oligonucleotide probes complementary to the most common mutations. We also found that the beta/gamma synthesis ratio in homozygous Hb E is similar to that of beta-thalassemia/Hb E and DNA analysis is the only method to distinguish these two conditions in the couple at risk of having either beta-thalassemia/Hb E or asymptomatic homozygous Hb E. In 100 pregnancies studied, the diagnoses were achieved in 96 pregnancies. Complications leading to fetal loss were found in 3 pregnancies: one woman developed amnionitis after fetal blood sampling; one had amniotic fluid leakage after the biopsy, and the third, carrying a normal fetus, aborted 10 days after fetal blood sampling with urinary tract infection and high fever. However, these figures are compatible with other reports and the risks are significantly lower than that of thalassemic disease the fetus is facing. One case of beta-thalassemia/Hb E was incorrectly diagnosed prenatally as being Hb E trait. In twenty-five pregnancies (25%) prenatally diagnosed to carry affected fetuses it was decided to have abortion. This study shows the feasibility of prenatal diagnosis for thalassemic diseases in Thailand which, in addition to screening and genetic counseling, can support prevention and control programs for thalassemia.

Pituitary function in thalassemic patients and the effect of chelation therapy

This study examined anterior pituitary function and the effect of chelation therapy in 31 patients with beta-thalassemia/HbE disease. Patients were divided into those receiving chelation therapy by deferoxamine and those receiving no such therapy (control group). Pituitary function studies were repeated in both groups 18 months later. The results showed decreased pituitary responses following stimulation in 22 patients. Among these, gonadotropin and PRL responses were most affected. After 18 months, serum ferritin levels had significantly decreased in the deferoxamine group. PRL and GH responses were improved in 3 patients receiving chelation therapy without changes in other hormone responses. In contrast, no changes in pituitary responses were shown in the control group at the end of follow-up. There were 6 drop-outs (4 in the control and 2 in the deferoxamine group) and 3 deaths (2 in the control and 1 in the deferoxamine group) during 18 months. In conclusion, gonadotropin and PRL deficiencies occur most frequently in thalassemic patients. Chelation therapy for 18 months markedly reduced serum ferritin level and might preserve or improve PRL and GH secretions, but seems to have no beneficial effects on other pituitary hormone reserves.

Ultrasonographic method for detection of haemoglobin Bart's hydrops fetalis in the second trimester of pregnancy

In nine pregnant women at risk for fetal alpha-thalassaemia, the two affected fetuses were diagnosed by ultrasonography at 18-20 weeks' gestation. In countries with limited resources, ultrasonography provides a cost-effective method of prenatal screening for this condition.

Hemoglobin Dhonburi alpha 2 beta 2 126 (H4) Val----Gly: a new unstable beta variant producing a beta-thalassemia intermedia phenotype in association with beta zero-thalassemia

While investigating the mechanism of a beta-thalassemia intermedia phenotype in a 34 year old Thai male, a new Hb variant beta 126 Val----Gly named Hb Dhonburi was discovered. Genetic and structural studies revealed the existence of a beta zero-thalassemia genotype in association with the beta variant. The new variant is unstable but exhibits normal oxygen binding properties. Hb Dhonburi was also discovered in the mother of the propositus in association with Hb E.

A novel C-T transition within the distal CCAAT motif of the G gamma-globin gene in the Japanese HPFH: implication of factor binding in elevated fetal globin expression

Hereditary persistence of fetal hemoglobin (HPFH) is a condition characterized by the continued expression of the fetal globin gene in adulthood. Both deletional and nondeletional forms have been described. We studied one Japanese family with two different nondeletional forms of HPFH. Analysis of polymorphic restriction sites in the beta-globin gene cluster suggested that one affecting both G gamma and A gamma globin expression in two members of the family could be associated with unknown conditions not linked to the beta-globin gene loci. Characterization by the polymerase chain reaction (PCR) of another form producing a G gamma-HPFH phenotype in two other members demonstrated a novel C-T transition at the nucleotide -114 within the distal CCAAT motif of the G gamma-globin gene. Using gel retardation assays on various nuclear extracts, we also demonstrated that this novel mutation abolishes the binding of the ubiquitous CCAAT binding factor, CP1 to the distal CCAAT motif of the gamma-globin gene but does not affect the binding of any erythroid specific factor, thereby suggesting a possible role for CP1 in the developmental regulation of fetal globin expression.

The molecular basis of beta-thalassemia in Thailand: application to prenatal diagnosis

To enable the prenatal diagnosis of beta-thalassemia by direct detection of the mutant beta-globin genes, we have determined the spectrum of mutations causing this disease in Thailand. The techniques employed included a combination of synthetic oligonucleotide probe hybridization, direct sequencing of genomic DNA enzymatically amplified by the polymerase chain reaction, and cloning and sequencing of the beta-globin genes. A total of 116 beta-thalassemia genes from 78 Hb E/beta-thalassemia patients and from 19 homozygous beta-thalassemia patients were analyzed, and the mutation was characterized in 112/116 (97%) of them. Eleven mutations were found, of which four (-CTTT in codon 41/42, AAG----TAG in codon 17, C----T in position 654 of the IVS-2 region, and A----G in position -28 upstream of the beta-globin gene) accounted for 83%; two previously undescribed mutations have been identified. The spectrum of beta-thalassemia mutations is similar to that reported among the Chinese. However, within the Thai population itself, patients with homozygous beta-thalassemia show a wider spread of mutations in comparison with the Hb E/beta-thalassemia group, in whom the frameshift 41/42 mutation predominates at a frequency of 62%. This difference in distribution may reflect the difference in ethnic origin of the two groups. Characterization of these mutations should aid the planning of a prenatal diagnosis program for beta-thalassemia in Thailand.

Molecular basis of HbE-beta-thalassemia and the origin of HbE in northeast Thailand: identification of one novel mutation using amplified DNA from buffy coat specimens

Amplification of DNA via polymerase chain reaction directly from a small amount of a buffy coat fraction was used to study the molecular basis of HbE-beta-thalassemia in the northeastern Thai population. Eight different mutations including the new one causing a beta o-thalassemia phenotype were detected. This novel mutation is an amber mutation at codon 26, which occurs at the same position as that of HbE; the most common hemoglobin variant in Southeast Asian countries. A pitfall in detection of the HbE mutation by restriction enzyme analysis was pointed out and differential diagnosis of the HbE mutation and the novel one by using allele specific oligonucleotide probes were described. Analysis of polymorphic restriction sites in the beta-globin gene cluster containing the beta E gene revealed two previously undescribed haplotypes in the Southeast Asian populations, which provide evidence for the multiple origins of beta E gene in Southeast Asian populations.

A single nucleotide deletion in codon 123 of the beta-globin gene causes an inclusion body beta-thalassaemia trait: a novel elongated globin chain beta Makabe

The beta-globin gene from a Japanese individual with an inclusion body beta-thalassaemia trait has been characterized by gene cloning and DNA sequencing. An adenine deletion was detected at the first position of codon 123 (ACCCC) of one allele whereas the other allele had a normal sequence. Heterozygosity for this mutation in the patient was confirmed by Southern blots of the genomic DNA digested with HphI, the recognition site of which is eliminated by this deletion. This one base deletion results in the shift of a reading frame in such a manner that the normal termination codon is out of phase. This frameshift mutation results in the synthesis of an elongated beta-globin chain with 10 extra amino acid residues and with an altered C-terminus. Analysis of labelled globin chains using CM-cellulose column chromatography failed to demonstrate any abnormal protein, thereby suggesting that the beta-globin chain variant is highly unstable and probably degrades rapidly after synthesis. This event will lead to an accumulation of free alpha-chains precipitating in the red blood cells and an inclusion body beta-thalassaemia phenotype would ensue.

Cardiac involvement in beta-thalassemia/hemoglobin E disease: clinical and hemodynamic findings

Clinical and hemodynamic studies were conducted in 6 women and 2 men with beta-thalassemia/hemoglobin E disease. All except one had splenectomy. The patients were hospitalized in the state of congestive heart failure. The systemic blood pressure was low or normal. The electrocardiograms revealed normal sinus rhythm in all, right axis deviation in some, right atrial enlargement in the majority and repolarization abnormalities in some. The echocardiograms were sensitive to detect the right heart abnormalities and pericardial effusion. Cardiac catheterization disclosed moderate to marked hypoxemia. All patients except one had pulmonary hypertension. Some had left ventricular dysfunction. From this study. It is concluded that right heart involvement secondary to diffuse pulmonary thromboembolic disease is a major complication of beta-thalassemia/hemoglobin E disease.

Molecular heterogeneity of beta-thalassaemia in the Japanese: identification of two novel mutations

Five unrelated Japanese beta-thalassaemia genes, from one homozygote and four heterozygotes, have been systematically characterized using DNA polymorphism analysis, polymerase chain reaction, dot-blot hybridization and direct sequencing of amplified genomic DNA. Four different molecular defects were observed on three different beta-globin gene frameworks. One of these, the A----G mutation in the TATA box, a previously described mutation, was detected by dot-blot hybridization in one homozygote and one heterozygote with the beta-globin gene of framework 2. The second mutation is a C----T substitution at position 654 of IVS-2, the mutation commonly found in Chinese, which was associated with the framework 1 gene. Another two mutations, both associated with framework 3 genes, are novel ones; an amber mutation in codon 90 (GAG to TAG) and a frameshift (+G) insertion in codon 54, both of which cause a beta 0-thalassaemia phenotype by premature termination of the beta-globin chain synthesis.

Molecular characterization and nonradioactive detection of beta-thalassemia in Malaysia

The spectrum of beta-thalassemia mutations in Malaysia has been determined in 45 beta-thalassemia chromosomes using dot blot hybridization of the polymerase chain reaction amplified DNA and direct DNA sequencing. Eleven different molecular defects, including those previously detected in Chinese, Asian Indians, and American blacks, and a novel frameshift mutation causing beta zero-thalassemia were detected. Since this novel mutation, a T deletion in codon 15 creates a new restriction site for EcoRII enzyme; the mutation could be detected by EcoRII digestion of the appropriate amplified fragment. The results of the present study provide additional information on the molecular heterogeneity of beta-thalassemia in this population. We also demonstrated the nonradioactive detection method of the beta-thalassemia mutation based upon the digoxigenin-labeled oligonucleotide probes.

Thai G gamma (A gamma delta beta)zero-thalassemia and its interaction with a single gamma-globin gene on a chromosome carrying beta zero-thalassemia

Clinical manifestations and hematologic data of thalassemia intermedia were observed in three siblings of a Thai family. Analyses of the hemoglobin of their parents and other siblings indicated that they inherited a delta beta-thalassemia gene from the father and a beta zero thalassemia gene from the mother. Globin gene mapping confirmed that they carry two abnormal beta-globin gene complexes. On one chromosome more than 70 kb of DNA was removed which resulted in G gamma (A gamma delta beta)zero-thalassemia. The deletion started at the Hind III site located just 3' to the G gamma gene, and extended downstream to a region recognized by the p3'N 2.8R probe which is located more than 45 kb from the 3' end of the beta gene. The other chromosome carried a beta zero thalassemia gene, and a 5 kb deletion between the G gamma and A gamma genes which produced a hybrid -GA gamma- gene. A synthetic oligonucleotide probe showed that this beta zero thalassemia arose from a C----T mutation at position 654 of IVS-II in the beta-globin gene.

Molecular basis of beta-thalassemia in Thailand: analysis of beta-thalassemia mutations using the polymerase chain reaction

beta-Thalassemia mutations in 71 chromosomes of Thai patients from the northeast, the middle and the south of the country were investigated using dot blot hybridization of PCR (polymerase chain reaction)-amplified DNA with allele-specific oligonucleotide probes. Eight different known molecular defects were detected, at different frequencies. There was an amber mutation in codon 17, a C-T transversion at position 654 of IVS-2, a frameshift mutation between codons 71 and 72, an A-G transition at nucleotide -28 within the TATA box (known as Chinese mutations), a G-T transversion at position 1 of IVS-1 (an Indian mutation), a 4 bp deletion in codons 41/42 and a G-C transversion at position 5 of IVS-1 (described as both Chinese and Indian mutations) and a Thai original mutation, an ochre mutation in codon 35. Analysis of the three unknown alleles by DNA sequencing of the cloned DNA fragment amplified by PCR revealed an A-G substitution at the second position of the codon for amino acid 19 (AAC-AGC). The analytic approach used in the present study and the characteristic distribution of mutations in each region of Thailand will prove useful for setting up a prenatal diagnosis program.

Study of mechanisms of post-transfusion hypertension in thalassaemic patients

Post-transfusion hypertension, convulsion and cerebral haemorrhage is a serious complication that may occur in the thalassaemias. In this study we evaluated the effect of blood transfusion on blood pressure, plasma renin activity (PRA), blood viscosity, and urinary vanillylmandelic acid (VMA) and catecholamines in 11 beta-thalassaemia/haemoglobin E patients. The results showed that after each unit of blood transfusion the blood viscosity was increased and correlated with the increased in haematocrit level. At the same time the PRA level was significantly decreased and tended to return to the normal level in a few days after the transfusion. There was no alteration in the urinary VMA and catecholamine levels. During the study two patients developed hypertension and headache. Their PRA were still lower than the pre-transfusion levels and the blood pressure returned to the normal pre-transfusion levels within 30-90 minutes after the intravenous injection of furosemide.

Molecular basis of beta (0)-thalassemia/HbE disease in Thailand

The molecular basis of beta(0)-thalassemia/HbE disease in 30 Thai patients was investigated using DNA amplification and dot-blot hybridization with a number of allele specific oligonucleotide probes. The mutations identified were 17 cases of 4 base-pair deletion at codons 41-42, 4 cases of amber mutation at codon 17, and one case each of an ochre mutation at codon 35, a single base substitution at position 5 of IVS-1, and a single base substitution at position 654 of IVS-2.

Detection of beta-thalassemia and hemoglobin E genes in Thai by a DNA amplification technique

Enzymatic DNA amplification and polyacrylamide gel electrophoresis, which demonstrate different sizes of DNA fragments, were used to detect the common mutations causing beta-thalassemia and hemoglobin (Hb) E in Thai people. The 4-bp deletion at codons 41 and 42 can be detected directly by polyacrylamide gel electrophoresis and ethidium bromide staining. Whereas the nonsense mutations at codon 17 (AAG----TAG) and Hb E (GAG----AAG at codon 26) were detected after digestion of the amplified DNA with the enzymes MaeI and MnlI, respectively.

Analysis of hematological data of thalassemia cases in Thailand

We analyzed the complete blood count (CBC) obtained from patients with various types of thalassemia in Thailand. As a control, samples from healthy donors and patients with iron deficiency anemia were also collected. Most cases of thalassemia could be differentiated from iron deficiency anemia by using a discrimination function equation. This screening method is applicable for mass-screening of patients with latent thalassemia in Thailand.

Laboratory diagnosis for thalassemia

Thalassemia is one of the common genetic disorders worldwide. alpha-thalassemia, beta-thalassemia, Hb E and Hb Constant Spring are common mutations found in S E Asia. The diagnoses of thalassemia and some abnormal hemoglobin carriers are very crucial for the identification of a high risk couple who will need further investigation of prenatal diagnosis. Determination of any thalassemic disease such as Hb H disease, homozygous beta-thalassemia, beta-thalassemia/Hb E can be carried out easily from the clinical findings, changes in hematologic data and hemoglobin electrophoresis. But the diagnoses of thalassemia carriers are cumbersome and sometimes need very sophisticated techniques of in vitro protein synthesis and DNA analysis. In this paper we review the laboratory methods and strategies for the diagnosis of thalassemia and abnormal hemoglobin commonly found in S E Asia.

A novel ochre mutation in the beta-thalassemia gene of a Thai. Identification by direct cloning of the entire beta-globin gene amplified using polymerase chain reactions

The beta-globin genes from a Thai patient compound heterozygous for beta-thalassemia and HbE disease were investigated. The 3.0-kilobase fragment containing the entire beta-globin gene was amplified by polymerase chain reaction, using Taq DNA polymerase followed by direct cloning of the amplified product into plasmid DNA. Sequence analysis of the thalassemia gene revealed only one base change, a C-A transversion within codon for an amino acid 35. This new mutation creates a premature terminator, TAA, an ochre codon, and results in a beta 0-thalassemia phenotype. The same result was obtained when this mutation was analyzed using a conventional cloning technique, direct sequencing of the amplified product, and hybridization with allele-specific oligonucleotide probes. No misincorporation was detected in the sequence analysis of the 3.0-kilobase insert of five clones of the amplified products obtained from genomic DNA of a normal individual. This approach is a rapid and accurate method for molecular cloning of the beta-globin gene and also other genes, the partial nucleotide sequences of which are known.

Selective enzymatic amplification of alpha 2-globin DNA for detection of the hemoglobin Constant Spring mutation

Hemoglobin Constant Spring is an elongation mutation of the alpha 2-globin locus that results in a thalassemic phenotype. It has a high prevalence in Asian populations. When inherited with other alpha-thalassemia determinants, the Constant Spring gene has the potential to cause severe forms of alpha-thalassemia. Accurate diagnosis of the condition with standard hemoglobin electrophoresis is unreliable due to the small to undetectable amounts of the mutant hemoglobin present. Because of the extensive sequence homology of the alpha 1 and alpha 2 loci, allele-specific hybridization to total genomic DNA containing the Constant Spring gene would not distinguish between heterozygous and homozygous hemoglobin Constant Spring. Selective enzymatic amplification of alpha 2-globin DNA sequences, however, allows unambiguous diagnoses to be made using allele-specific hybridization. This method is useful for providing accurate genetic counseling and prenatal diagnosis in populations and specific families in which precise diagnosis is important.

Heterogeneity of the gamma-globin gene sequences in Japanese individuals: implication of gene conversion in generation of polymorphisms

The linked fetal globin genes (the G gamma- and A gamma-globin genes) were cloned from Japanese individuals with three different haplotypes of the HindIII polymorphisms within the gamma-globin genes. Determination of nucleotide sequences of the segment spanning from IVS2 to the 3' flanking region of each gamma-globin gene revealed that nucleotide differences are located at 43 positions and a stretch of simple GT or GC sequences. Almost half of the nucleotide changes could be accounted for by gene conversion between the G gamma- and A gamma-globin genes. We found that gene conversion had created the SacI polymorphic site just downstream of the A gamma-globin coding region. Association of the SacI polymorphic site with the HindIII polymorphic site suggests that the region containing these two sites was derived from that of the linked G gamma-globin gene through a gene conversion event. The nucleotide sequences obtained here are identical to those of the Caucasoid fetal globin genes of the same haplotypes, with the exception of some sequence changes in the hot spots of mutations. These results indicate that the sequence heterogeneity of the gamma-globin genes can be classified into three major categories according to HindIII haplotypes. The possible mechanisms of generation of the heterogeneity of the gamma-globin gene sequences are discussed.

Decreased sensitivity of artesunate and chloroquine of Plasmodium falciparum infecting hemoglobin H and/or hemoglobin constant spring erythrocytes

Plasmodium falciparum infecting hemoglobin (Hb) H and/or Hb Constant Spring erythrocytes in vitro was relatively more resistant than that infecting normal erythrocytes to artesunate and chloroquine, while the sensitivity to pyrimethamine was unchanged. The 50% inhibitory concentrations (IC50) for artesunate in HbH (alpha-thal 1/alpha-thal 2), HbH (alpha-thal 1/Hb Constant Spring), and homozygous Hb Constant Spring erythrocytes were 4.5 +/- 2.8, 8.5 +/- 3.2, and 2.6 +/- 1.6 nM compared with 0.82 +/- 0.35 nM in normal erythrocytes (P less than 0.002 for all three cases). The IC50 for chloroquine were 97 +/- 46, 162 +/- 67, and 93 +/- 36 nM, respectively, in the variant erythrocytes, compared with 48 +/- 13 nM in normal erythrocytes (P less than 0.002, 0.002, and 0.02, respectively). The differences in sensitivity to artesunate and chloroquine of the parasite infecting HbH erythrocytes are probably related to their oxidative mode of action and relatively high amounts of antioxidant enzymes in the host erythrocytes. This novel example of dependence on the host of the malarial parasite drug sensitivity may have implications for chemotherapy of malaria in patients with genetically variant erythrocytes.

Cytochemical evaluation of neutrophil components in beta thalassemia hemoglobin E

The mean +/- S.D. of LAP score in neutrophil of the normal control, non splenectomised patients and splenectomised patients were 116 +/- 78, 94 +/- 48 and 37 +/- 23 Kaplow units, respectively. The significant reduction in the leukocyte alkaline phosphatase level (P less than 0.05) was found in beta thalassemia/HbE patients. The degree of reduction was greater in the splenectomised patients (P less than 0.05). The decreased LAP levels in PMN was persistent. This was in contrast to the LAP in PMN of other patients where as LAP returned to normal after splenectomy. The relevance to the increased susceptibility to infection and low LAP in beta thalassemia/HbE should be further investigated.

The molecular basis of AE-Bart's disease

AE-Bart's disease is a thalassemia intermedia resulting from the interaction between alpha-thalassemia and heterozygous Hb E. In this study we analyzed the alpha-globin genes of 25 patients designated as AE-Bart's disease by starch gel electrophoresis. Twenty-one cases had Hb Constant Spring in addition to Hbs E + A + Bart's, and the remaining four cases had only Hbs E + A + Bart's. DNA mapping revealed the alpha-globin genotype of alpha-thalassemia-1/alpha-thalassemia-2 in four patients who had Hbs E + A + Bart's, whereas the alpha genotype of the remainder is alpha-thalassemia-1/nondeletion alpha-thalassemia. The nondeletion alpha-thalassemia is Hb Constant Spring as indicated by starch gel electrophoresis. Hematologic data and hemoglobin analysis showed that Constant Spring-AE-Bart's disease is a more severe clinical syndrome than AE-Bart's disease.

Effects of thalassaemic serum on the in vitro development of the malarial parasite Plasmodium falciparum

Sera from thalassaemic individuals were experimentally tested for their suppressive effects on the in vitro development of asexual stages of Plasmodium falciparum. Cultures in sera collected from six patients who had classical haemoglobin H disease (alpha-thal1-alpha-thal2) and six patients who had haemoglobin H disease with haemoglobin (Hb) Constant Spring (alpha-thal1-CS) showed a significantly higher degree of inhibition of parasite multiplication than cultures of thalassaemic erythrocytes in sera from healthy individuals. Similarly, sera from 12 patients with beta-thalassaemia/haemoglobin E (beta-thal-HbE) diminished parasite development in vitro. Schizonts of P. falciparum cultured in erythrocytes from non-thalassaemic individuals containing normal Hb (alpha 2 beta 2) were also inhibited when thalassaemic serum was used in place of normal serum. The degree of inhibition was proportional to the concentration (vol/vol) of the thalassaemic serum.

Hematologic changes in alpha-thalassemia

Alpha-thalassemia is very common in Thailand. Interaction of the different types of alpha-thalassemia can lead to many alpha-thalassemia syndromes. In this study the authors compare the hematologic data of subjects with various alpha-thalassemia phenotypes. Designation of the genotypes was based on family study and DNA mapping. The results show that there are equivocal hematologic findings among those who have similar molecular defects, i.e., alpha-thalassemia-2 and hemoglobin (Hb) Constant Spring heterozygotes: alpha-thalassemia 1, homozygous alpha-thalassemia 2, and alpha-thalassemia 2/Hb Constant Spring. The severity of these alpha-thalassemia syndromes correlates with the alpha-globin gene expression calculated from the finding of Liebhaber (Liebhaber SA, et al. J Biol Chem 1986; 261:15327-15333).

Impaired parasite growth and increased susceptibility to phagocytosis of Plasmodium falciparum infected alpha-thalassemia or hemoglobin Constant Spring red blood cells

In vitro multiplication of Plasmodium falciparum in hemoglobin H or hemoglobin Constant Spring red blood cells (from homozygotes or double heterozygotes) was significantly reduced as compared with that in normal erythrocytes. The parasitized genetically abnormal red blood cells showed furthermore a high propensity for being phagocytosed by peripheral blood monocytes. Both impaired parasite growth and increased susceptibility to phagocytosis may be related to mechanisms for protection of the variants from P. falciparum infection.

The effect of erythroid hyperplasia on iron balance

Measurements of erythropoiesis and iron balance were made in eight normal and 32 anemic subjects. The latter consisted of 12 individuals with ineffective erythropoiesis (beta-thalassemia/hemoglobin E), 13 subjects with ineffective erythropoiesis and hemolytic anemia (hemoglobin H), and seven subjects with hemolytic anemia (hereditary spherocytosis). A consistent relationship within each group existed between the degree of erythropoiesis and radioiron absorption. Although the effect of erythropoiesis on iron absorption was of similar magnitude in the two thalassemia groups, the effect in hereditary spherocytosis was much less. There was agreement between absorption and ferritin or magnetic susceptibility (SQUID) measurements of iron stores in thalassemia, but in hereditary spherocytosis a discrepancy existed between absorption and ferritin. It is concluded that, although increased erythropoiesis is associated with increased iron absorption, some additional factor associated with red cell breakdown is more directly responsible for the positive iron balance in thalassemia.

Differentiation of Plasmodium falciparum clones by means of a repetitive DNA probe

A recombinant DNA probe, pBRK1-14, was constructed by inserting a repetitive DNA fragment of 753 base pairs obtained from Plasmodium falciparum, isolate K1, into the EcoRI/PstI cloning sites of pBR322. This probe could discriminate between different parasite clones derived from a single isolate by hybridization with Southern genomic blots.

EF Bart's disease: interaction of the abnormal alpha- and beta-globin genes

EF Bart's disease is an uncommon form of thalassaemia intermedia resulting from the co-inheritance of alpha-thalassaemia and haemoglobin E in the same subject. Starch-gel electrophoresis revealed two phenotypes in 19 patients with EF Bart's. 16 patients had Hbs CS + E + F + Bart's and the remainder had Hbs E + F + Bart's. DNA mapping and haemoglobin electrophoresis indicated that there are four genotypes, involving 5 abnormal globin genes, responsible for this thalassaemia syndrome.

Cord blood study on beta-thalassemia and hemoglobin E

We describe hematologic data from 18 newborn infants including follow-up data. Of these, ten were the offspring of patients with beta-thal/Hb E disease and the remainder were infants who were found to have a decrease in red cell osmotic fragility during a random cord blood examination. The results of the cord blood study showed that two infants having normal red cell osmotic fragility with about 2% Hb E + Hb A + Hb F at birth represented Hb E heterozygosity. Eleven babies had slightly decreased red cell osmotic fragility, a mild degree of microcytosis and poikilocytosis, and hemoglobin types of Hb A + Hb F with no elevation of Hb A2 at birth. They subsequently had hematologic findings consistent with the beta-thal heterozygosity. The means of hematological values of cord blood in the beta-thal trait infants appeared to be statistically different from those in the normal infants only with respect to increased red cell count and reduced MCH. One infant was thought to have the beta-thal trait but had a greater degree of thalassemic changes in red cells; subsequently he turned out to have homozygous beta-thalassemia. Four newborn infants with hypochromia and numerous target cells had 4-7% Hb E + Hb F without Hb A. Follow-up examination showed two cases of Hb E homozygosity; however, the others, who had obvious microcytosis and poikilocytosis in cord blood, finally developed beta-thal/Hb E disease. Thus, a careful study on red cell osmotic fragility, morphology and starch gel electrophoresis at birth allows detection and diagnosis of beta-thal heterozygosity, beta-thal homozygosity, Hb E heterozygosity, Hb E homozygosity and double heterozygosity for beta-thal and Hb E.

Beta-thalassemia associated with alpha-thalassemia in Thailand

In Thailand alpha-thalassemia (thal), beta-thal, hemoglobin (Hb) E and Hb Constant Spring (Hb CS) are prevalent. The incidences are 20-30% for alpha-thal (3.5% for alpha-thal-1 and 16% for alpha-thal-2), 3-9% for beta-thal, up to 54% for Hb E and nearly 8% for Hb CS. Different combinations of these genes result in a spectrum of thalassemia syndromes ranging in severity from asymptomatic to intrauterine death. From the known gene frequencies the numbers of thalassemic patients per generation (total population of 50 million) are as follows: Hb Bart's hydrops fetalis 20,000; homozygous beta-thal 31,250; beta-thal/Hb E disease 162,500; Hb H disease (two genotypes) 200,000, making a total of 413,750. In addition, individuals may carry more than two of the abnormal genes leading to complex thalassemia syndromes such as alpha beta-thal, AE-Bart's and EF-Bart's diseases.

Alpha-thalassemia in Thailand

The alpha-thalassemia syndromes are remarkable both for their phenotypic diversity and for their different clinical severity. They are associated with variable degrees of alpha-chain deficits; the clinical manifestations range from asymptomatic cases with normal hematologic findings to the totally lethal Hb Bart's hydrops fetalis syndrome. Recent molecular biology studies have clarified the defects in these alpha-thalassemia syndromes around the world. This paper describes the alpha-thalassemias in Thailand, and covers the types, molecular defects, incidence of each genotype, and their phenotypic expression.