P. Wasi

Alpha- and beta-thalassemia in Thailand.

In Thailand, both aand P-thalassemia are widespread and there is more than one subtype in each variety. Hemoglobin (Hb) E which is a2, p;6Gu+Lys (Hunt & Ingram, 1959) is remarkably frequent (Na-Nakorn et al . , 1956; Sundharagiati et al., 1958, 1959a, 1959b; Flatz et al., 1965; Wasi et al., 1967a), reaching 50 percent in certain areas. These abnormal genes in different combinations result in a spectrum of syndromes ranging from asymptomatic heterozygotes to lethal H b Barts hydrops fetalis. Attempts have been made to characterize the various genotypes by clinical, hematologic, biochemical, genetic and cord blood studies. This paper summarizes the manifestations of these syndromes, with particular emphasis on the diseased forms.

The Pattern of Disordered Haemoglobin Synthesis in Homozygous and Heterozygous β-Thalassaemia*

The rate of globin chain production has been studied in patients with homozygous β‐thalassaemia, heterozygous β‐thalassaemia, haemoglobin E‐thalassaemia, and sickle‐cell‐thalassaemia, and compared with that in non‐thalassaemic individuals. A partial or total deficit of β‐chain synthesis has been demonstrated in all forms of β‐thalassaemia. This results in the production of a large intracellular pool of α‐chains, the kinetics of which have been worked out. The α‐chains in this pool appear to contain haem and are unstable, rapidly becoming associated with the stromal fraction. These findings are examined in terms of the pathogenesis of the anaemia of thalassaemia.

Severity differences in β‐thalassaemia/haemoglobin E syndromes: implication of genetic factors

Summary. Genetic factors determining the difference in severity of anaemia in β‐thalassaemia/HbE disease were studied in 90 patients who had haemoglobin levels, at steady state, ranging from 4.2 to 12.6 g/dl. Co‐inheritance of α‐thalassaemia 2 and haemoglobin Constant Spring could significantly decrease the severity of the disease. Inheritance of a β‐thalassaemia chromosome with Xmn I cleavage site at position — 158 of the Gγ‐globin gene which was linked to the haplotype ‐ + ‐ ++ or ++ ‐ ++, was associated with a milder anaemia. Two copies of these alleles were necessary to produce a significant clinical effect. Increased expression of the Gγ‐globin gene and higher production of haemoglobin F. which could reduce the overall globin chain imbalance, were also associated with homozygosity for the Xmn I cleavage site and thus with less severe anaemia. However, this effect was not seen in Xmn I site heterozygotes. Whether the effects of the Xmn I polymorphism, HbF concentration and Gγ/Aγ ratio act separately or through common mechanisms in reducing anaemia remains to be ascertained.

Thalassemia in Thailand.

In Thailand, a and B thalassemia, hemoglobin (Hb) E, and Hb Constant Spring (Con Sp) are The frequencies are 20%-30% for a thalassemia, 3%-9% for thalassemia, up to 52% for Hb E and at least 4% for Hb Con Sp. The abnormal genes in different combinations lead to over 60 thalassemic syndromes. TABLE 1 shows the numbers of patients with major thalassemic diseases examined in our unit, exclusive of the Hb Barts hydrops fetalis. This is in the department of medicine; in the department of pediatrics of this hospital they have seen more or less the same numbers of thalassemic patients. Clinical features, although of extreme interest, will not be described here; however, certain other salient points will be discussed.

Identification of five rare mutations including a novel frameshift mutation causing β0-thalassemia in Thai patients with β0-thalassemia/hemoglobin E disease

Abstract 6 out of 14 uncharacterized β-thalassemia alleles from 187 Thai β-thalassemia/HbE patients were identified by direct sequencing of DNA amplified by polymerase chain reaction. A novel mutation occuring from an insertion of adenosine in codon 95, which results in a shift of the reading frame with the terminator at the new codon 101, was detected in one patient. In addition, two frameshift mutations not previously reported among the Thai population were also detected in 3 patients: one with a deletion of thymidine in codon 15 and two with an insertion of cytidine in codons 27/28. A frameshift mutation that occurred from a cytidine deletion in codon 41 was also found in one patient in this study. The remaining case was as amber mutation, GAG-TAG, in codon 43 in exon 2 of the β-globin gene. These mutations bring the number of mutations known to be present in the Thai population to a total of 20, 15 of which were detected in β-thalassemia/HbE patients.

The Thai variant and the distribution of alleles of 6-phosphogluconate dehydrogenase and the distribution of glucose 6-phosphate dehydrogenase deficiency in Thailand

The samples were taken from 3185 subjects from ten provinces throughout Thailand. In 1577 males the frequency of glucose 6-phosphate dehydrogenase deficiency was 11.98%. In the far south the gene frequency was 2.83%; in the remainder of the country the frequency did not vary significantly about a mean of 13.76%. The deficiency is of a severe type. The G6PD of all of the nondeficient individuals had the electrophoretic mobility of type B. The mean frequency of the A/B electrophoretic phenotype of 6-phosphogluconate dehydrogenase is 8.47%. The maximum frequency was in central and southern Thailand with a decline to the north and northeast. A variant form of 6-PGD, referred to as the Thai variant, has been found in which two additional electrophoretic components migrate anodally to the normal A band, confirming that the molecule is at least a dimer. The hypothesis is advanced that erythrocyte 6-PGD is determined by two genetic loci, only one of which is translated in leukocytes.

Haemoglobin J-Bangkok: a clinical, haematological and genetical study.

A Thai family with haemoglobins A + J‐Bangkok in nine persons is described. This rare abnormal pigment had identical electrophoretic mobility to other haemoglobins J, but, as α2β256Asp, is not similar to any previously described haemoglobin. Carriers of this haemoglobin were clinically and haematologically normal except for the presence of 47.4–67.2 per cent Hb J. It was also possible to follow the increment of Hb J‐Bangkok from 16.15 per cent in the cord blood to 46 per cent at 2½ months and to 55.18 per cent at 1 year of age. One person is believed to harbour both an α‐thalassaemia and Hb J‐Bangkok genes without evidence of interaction.

EF Bart's disease: Interaction of the abnormal α‐ and β‐globin genes

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

Incidence of haemoglobin Thai: a re-examination of the genetics of α-thalassaemic diseases

Haemoglobin (Hb) H disease is a mild to severe a-thalassaemic disease, characterized by the haemoglobin types of A + H and intra-erythrocytic inclusion bodies. The latter are aggregated masses of Hb H (/I4). This disease has been reported from many parts of the world, but is especially common among the Thai and the Chinese. Over 400 patients have been examined by us, not including more cases in the Department of Paediatrics of this hospital. The genetics of Hb H disease is peculiar, Hb H being not detectable in either parent in the majority of cases. It has been suggested (Wasi, Na-Nakorn & Suingdumrong, 1964; Huehns, 1965) that this disease results from double heterozygosity between a severe a-thalassaemia gene (a-thal,) and a milder allele (a-thal,). a-thal, leads to a complete, while a-thal, to a partial, suppression of a-chain synthesis. Homozygosity for a-thal, results in Hb Barts hydrops foetalis in which no Hb A is synthesized (Weatherall, Clegg & Wong, 1970; Todd et al. 1970). Further evidence (Na-Nakorn et al. 1969; Na-Nakorn & Wasi, 1970) supports the hypothesis of a-thal, and a-thal,. A haemoglobin, slower than Hb A, in starch-gel electrophoresis in alkaline pH, in association with a-thalassaemic diseases, was first reported from this laboratory in 1967 (Wasi et al. 1967) and again in 1968 (Wasi et al. 1969). This was found by Dr E. R. Huehns to be an a-chain variant, and has been named Hb Thai (Wasi, 1970b). Hb Thai constitutes only 1-2 % or less of the total haemoglobin. Thus it often escapes detection. The reason for its presence in such a small amount is yet to be shown, but it is very likely that this is due to decreased synthesis. Hb Thai gene, with almost complete suppression of a-chain synthesis, thus would have an a-thalassaemia-like effect. Double heterozygosity between Hb Thai gene and an a-thalassaemia gene should lead to a Hb H disease with the presence of a small amount of Hb Thai. The prevalence of Hb Thai among a-thalassaemic diseases has never been reported before. This should be very important in understanding the genetics of a-thalassaemia. We wish to report the incidence of Hb Thai among patients with Hb H disease. b

Hereditary Persistence of Foetal Haemogloblll in a Thai Family: The First Instance in the Mongol Race and in Association with Haemoglobin E

Summary. Hereditary persistence of foetal haemoglobin is described in a Thai family. The AF heterozygotes were healthy and had normal haematological findings except the decrease in haemoglobin A2 level and the presence of a large amount of haemoglobin F. The latter, comprising 21–22 per cent, is higher than in the Greek but lower than in the Negro counterparts. Three persons, who were heterozygous for both haemoglobin E and high F genes, were not anaemic but had numerous target‐erythrocytes; haemoglobin E constituted 40 per cent, the rest being haemoglobin F. Acid‐elution staining revealed haemoglobin F in every red cell in both AF and EF heterozygotes. The absence of haemoglobin A in the latter suggests allelism between this type of hereditary persistence of foetal haemoglobin and haemoglobin E or β‐structural gene.