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.

Inhibitory effect of beta zero-thalassaemia/haemoglobin E erythrocytes on Plasmodium falciparum growth in vitro

The growth of Plasmodium falciparum in erythrocytes from individuals with beta zero-thalassaemia or haemoglobin (Hb) E, or both, was assessed in vitro. A significant inhibitory effect on the growth of the parasite was found only with erythrocytes from individuals doubly heterozygous for beta zeros-thalassaemia and HbE. The inhibitory effect was particularly marked with erythrocytes from splenectomized beta zeros-thalassaemia/HbE patients. The protective effect was related to HbF, Hb levels and shape abnormalities of the variant erythrocytes.

Different severity of homozygous beta-thalassemia among siblings

Different degrees of severity of anemia are presented in three siblings with homozygous beta-thalassemia. II-1, the most severely affected one, is splenectomized and needs frequent blood transfusion, while II-4 has mild anemia and never receives transfusion. II-3 has moderate anemia and mild jaundice and hepatosplenomegaly. Restriction endonuclease DNA mapping revealed the alpha-thalassemia-2 genes in II-3 and II-4 and no alpha-thalassemia-2 haplotype in II-1. Furthermore, II-4, who is mildly affected, is homozygous for alpha-thalassemia-2 whereas II-3 is an alpha-thalassemia-2 heterozygote. These observations indicate that concomitant inheritance of alpha-thalassemia can decrease the severity of beta-thalassemia.

Defective spectrin dimer self-association in thalassemic red cells

The relative proportions of spectrin tetramer and dimer forms extrated from red cell membranes in a low ionic strength buffer at 4 degrees C were determined for 15 normal subjects, 27 subjects with alpha-thalassemia (7 alpha-thalassemia trait, 9 Hb H disease (alpha-thal 1/alpha-thal 2) and 11 Hb H with Hb Constant Spring (CS), 23 subjects with beta-thalassemia (6 beta-thalassemia trait, 5 homozygous beta-thalassemia, 11 beta(0)-thalassemia with Hb E and 1 beta(+)-thalassemia with Hb E), 6 subjects with Hb E (2 homozygous and 4 carriers) and 1 subject with combined alpha-thal 1/Hb CS and Hb E (AE Bart's disease). In all subjects (except carriers of Hb E and 1 splenectomized case of beta(0)-thal/Hb E) spectrin dimer forms were elevated when compared to levels in normal controls, but there were no significant differences between carrier and disease forms. Conversion of spectrin dimers to tetramers at 30 degrees C was reduced in the thalassemic subjects with disease but was within normal range for thalassemic carriers.

Identification of Hb Lepore-Washington-Boston in association with Hb E [beta 26(B8)Glu----Lys] in a Thai female

The proposita was a Thai female showing signs of a mild anemia (Hb: 11.4 g/dl; RBC: 4.91 X 10(6)/mm3; reticulocytes: 2.4%; MCV: 70 fl; MCHC: 23.3 g/dl). Hemoglobins were isolated by DEAE-cellulose chromatography in the following relative amounts: Hb E + Hb A2 = 53%; Hb F0 = 30.0%; Hb delta beta-Lepore = 12.7%; Hb F1 = 4.3%. The beta E and delta beta-Lepore chains were isolated by CM-cellulose chromatography and were subjected to tryptic peptide mapping on paper in comparison to normal beta A chains. Amino acid analysis of selected peptides permitted unambiguous identification of the abnormal hemoglobins as Hb E [beta 26(B8)Glu----Lys] and Hb Lepore-Washington-Boston, which has a delta chain sequence for residues 1-87, and a beta chain sequence for residues 116-146. The presence of a Lepore hemoglobin was further confirmed by Pst I digestion of the proposita's DNA. The association of the two hemoglobin variants gave rise to elevated levels of Hb F.

Thalassemic erythrocytes inhibit in vitro growth of Plasmodium falciparum

Blood specimens from 100 thalassemic patients were screened in vitro for inhibitory effects on growth and multiplication of Plasmodium falciparum. The culture medium mixture designated REM consisted of 9 volumes of minimum essential medium (GIBCO Laboratories, Grand Island, N.Y.) and 1 volume of RPMI 1640 (GIBCO) supplemented with 10% heat-inactivated human serum. Parasite multiplication in erythrocytes containing normal hemoglobin cultured in RPMI or REM was similar. Significant reduction in parasite multiplication rates was observed in erythrocytes containing abnormal hemoglobin when these were cultured in REM. The degree of reduction in five types of thalassemic erythrocytes was in the following descending order: hemoglobin H disease with Hb Constant Spring, classical hemoglobin H disease, beta(0)-thalassemia-hemoglobin E in which blood harbored a high percentage of hemoglobin F-containing cells, beta (0)-thalassemia-hemoglobin E in which blood harbored few hemoglobin F-containing cells, and beta-thalassemia heterozygous variant.

Comparison of erythrocyte antioxidative enzyme activities between two types of haemoglobin H disease

The activities of erythrocyte antioxidative enzymes were measured in two groups of patients with different genotypes of haemoglobin (Hb) H disease: 21 with alpha-thalassaemia 1 or alpha-thalassaemia 2 (alpha-thalassaemia 1/2) and 21 with alpha-thalassaemia 1/Hb Constant Spring (HbCS). They were compared with 21 normal subjects. Both genotypes of Hb H disease had increased activities of erythrocyte superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase when compared with those of controls. Comparison of the two genotypes showed that subjects with alpha-thalassaemia 1/Hb CS, the more severe disease, had higher SOD and GSH-Px activities but lower catalase activity than those with alpha-thalassaemia 1/2. This indicates that there are compensatory mechanisms in Hb H erythrocytes to cope with increased generation of oxygen free radicals as a result of increased excess beta chain.

Studies of erythropoietic cells in heterozygotes and homozygotes for haemoglobin Constant Spring and in heterozygotes for both haemoglobin Constant Spring and alpha-thalassaemia 1 trait: extent of globin chain precipitation and cell cycle distribution

Electron microscope studies revealed that the average value for the percentage of erythropoietic cell profiles containing globin chain precipitates in heterozygotes for haemoglobin Constant Spring (HbCS) was similar to that in subjects with alpha-thalassaemia 2 trait and that the average values for this parameter in homozygotes for HbCS and patients with HbCS-H disease were similar to that in individuals with HbH disease. The explanation for the finding that the presence of two alpha cs genes (in homozygotes for HbCS) caused a degree of precipitation corresponding to that seen in patients with HbH disease, who have three deleted alpha genes, rather than to that seen in individuals with alpha-thalassaemia 1 trait, who have two deleted alpha genes, is uncertain. In all the patients with HbCS studied, the majority of the inclusions of precipitated globin chains had a stellate or branching appearance and were considered to consist of beta-chains. However, in the homozygotes for HbCS and to a lesser extent in the patients with HbCS-H disease there were small but significant numbers of erythropoietic cell profiles containing multiple rounded inclusions of the type seen in the beta-thalassaemia syndromes, or both branching and multiple rounded inclusions. It is argued that these rounded inclusions probably consisted either of precipitated HbCS or beta-chains rather than alpha-chains. The distribution of erythroblasts in the different stages of the cell cycle was normal in two homozygotes for HbCS and two patients with HbCS-H disease, indicating that there was little or no cell death during the proliferative phase of erythropoiesis in either of these conditions.

Increased phagocytosis of Plasmodium falciparum-infected erythrocytes with haemoglobin E by peripheral blood monocytes

Erythrocytes from subjects with homozygous and heterozygous haemoglobin E (HbE) infected with Plasmodium falciparum in vitro were phagocytosed to a greater extent by normal human monocytes than infected erythrocytes from normal subjects. Susceptibility to phagocytosis was maximal when the parasites developed to trophozoite and schizont stages in both normal and patients' erythrocytes. The increased susceptibility of P. falciparum-infected HbE erythrocytes to phagocytosis by monocytes may play a role in protection against malaria.

Prevalence of HTLV-III/LAV antibody in selected populations in Thailand

Antibody to the human T-lymphotropic virus, type III/lymphadenopathy-associated virus (HTLV-III/LAV) by ELISA test was detected in one (1%) of 101 male homosexual prostitutes (confidence limit 95%:0.03-5.4%, in two (2%) of 100 thalassemia patients, and in none (C.L. 95%:0-3.6%) of 100 female prostitutes, 99 parenteral drug abusers, 100 male VD patients, 100 consecutive blood donors in serum collected from February through June 1985. Serum from the positive homosexual subject was strongly positive on repeated ELISA testing, and was also positive by Western Blot test. The two thalassemia patients, who were repeatedly weakly-positive by ELISA, were negative by Western Blot test and presumed to be false positive reactors. Prevalence of HTLV-III/LAV virus in sexually-active homosexuals in Thailand in 1985 appears to be similar to the 1% rate among homosexuals in San Francisco in 1978 at the start of the AIDS epidemic there.

Concomitant inheritance of alpha-thalassemia in beta 0- thalassemia/Hb E disease

Concomitant inheritance of alpha-thalassemia in patients with beta 0-thalassemia/hemoglobin (Hb) E disease was detected by restriction endonuclease DNA mapping. Among 42 patients with beta 0-thalassemia/Hb E disease, seven were found to have an alpha-thalassemia-2 haplotype. Of these, five belonged to the rightward or 3.7-kb type of alpha-thalassemia-2 and the remaining two the leftward or 4.2-kb type. All the seven patients with alpha-thalassemia-2 haplotype had hemoglobin levels of 7.4 g/dl or above; those without detectable alpha-thalassemia had hemoglobin levels both higher and lower than 7.4 g/dl. The latter attended the clinic regularly, the former did occasionally. These findings suggest that concomitant inheritance of alpha-thalassemia can alleviate the severity of beta 0-thalassemia/Hb E disease. Failure to find alpha-thalassemia-1 haplotype in these patients suggests that concomitant inheritance of alpha-thalassemia-1 with beta 0-thalassemia/Hb E might lead to so mild a condition that the individuals do not present clinically. The fact that many patients without a detectable alpha-thalassemia haplotype also had hemoglobin levels of 7.4 g/dl or higher suggests that there are additional factors responsible for the mildness of beta 0-thalassemia/Hb E disease.

Thalassemia in southeast Asia: determination of different degrees of severity of anemia in thalassemia

beta (0)-Thalassemia/Hb E in Southeast Asia varies greatly in severity, with hemoglobin levels ranging from 2.5 to 13.5 g/dl, averaging 7.7 g/dl. Results of systematic investigations to find out what determines different levels of severity are reviewed. Concomitant inheritance of alpha-thalassemia significantly decreases the severity. Different degrees of severity in the majority of cases, however, is not due to alpha-thalassemia. Concordance of hemoglobin levels among patients who are sibs prevails, suggesting polygenic factor determinants. Potential factors ruled out as determinants for different levels of severity are discriminating fetal hemoglobin production, erythrocyte superoxide dismutase activity, reticulo-endothelial function, and failure of erythropoiesis compensation. Red cell survival and globin synthesis studies indicate that different degrees of excess of alpha-chains leading to different red cell pathology and survival are responsible for variable severity. Degrees of excess of alpha-chains in this circumstance are probably mainly determined by erythrocyte proteolytic activity. The relationship between the hemoglobin levels and erythrocyte cytosol proteolytic activity in 15 beta(0) -thalassemia/Hb E disease patients in whom a deletional type of alpha-thalassemia had been ruled out by DNA mapping is striking, with a correlation coefficient of 0.78. This finding suggests that modulation of erythrocyte proteolysis is another approach for treatment of thalassemia.

Intracranial extramedullary hematopoiesis inducing epilepsy in a patient with beta-thalassemia--hemoglobin E

Generalized epileptiform seizures developed in a 23-year-old patient with beta-thalassemia-hemoglobin E. A computed tomographic scan suggested an intracranial mass. Surgery disclosed an extramedullary hematopoietic mass compressing the brain. Removal of the mass followed by irradiation of the area resulted in disappearance of the convulsions.

Cardiac pathology in 47 patients with beta thalassaemia/haemoglobin E

Autopsy protocols and heart slides of 47 patients with beta thalassaemia/haemoglobin E disease were reviewed. All but 1 patient had cardiac hypertrophy, accompanied by dilatation in 17; 5 of 9 patients (56%) with right ventricular and 11 of 22 patients (50%) with biventricular hypertrophy had chronic pulmonary thromboembolism. Cardiac iron deposition while present in 15 patients (32%) was very slight, in contrast to the amount of iron in their liver and pancreas. Four patients had fibrinous pericarditis, 2 with rheumatic heart disease. Twelve patients had chronic pericardial changes, 7 with adhesive pericarditis. The effects of cardiac pathology on the morbidity and mortality of patients with beta thalassaemia/haemoglobin E disease were discussed.

Determination for different severity of anemia in thalassemia: concordance and discordance among sib pairs

The degree of anemia in beta(0)-thalassemia/hemoglobin E disease is highly variable. As part of an attempt to identify determinants of this variability of severity we studied concordance and discordance of hemoglobin levels among sib pairs. The distribution of differences of hemoglobin levels in 216 sib pairs from 98 families showed a remarkable skewness toward the lower values with a mode at 0-0.5 gm/dl. The prevailing concordance of hemoglobin levels in patients from the same families and the persistence of the patterns indicate that polygenic factors are mainly responsible for the variability of anemia in this disease.

Ultrastructure and cell cycle distribution of erythropoietic cells in heterozygotes and homozygotes for haemoglobin E

Marrow aspirates from heterozygotes and homozygotes for haemoglobin E (HbE) have been studied by electron microscopy and by the technique of combined Feulgen microspectrophotometry and 3H-thymidine autoradiography. The erythropoietic cells of heterozygotes did not contain any precipitated globin chains and the proliferating erythroblasts of such individuals showed no abnormality in their distribution in the different stages of interphase. By contrast, 0-1.5% of late erythroblast profiles and 3.1-12.8% of marrow reticulocyte profiles of homozygotes contained intracellular inclusions resembling precipitated alpha-chains. Although precipitated globin chains were not seen in the early polychromatic erythroblasts of homozygotes, the number of these cells in the G2 phase relative to that in the S phase was increased. These data indicate that there is probably little or no imbalance of globin chain synthesis in heterozygotes, a substantial degree of imbalance in homozygotes, and a disturbance of erythroblast proliferation in homozygotes which cannot be attributed to the deleterious effects of detectable intracellular alpha-chain precipitates. The electron microscope and cell cycle distribution data in the homozygotes for HbE were similar to those in two heterozygotes for beta thalassaemia.

Hematologic and biosynthetic studies in homozygous hemoglobin Constant Spring

The elongated alpha-globin chains of hemoglobin Constant Spring (alpha cs chain of HbCS ) are produced in low amounts such that the alpha cs-gene acts as a form of alpha-thalassemia; yet in the homozygous state the pathophysiological effects of this mutant are more severe than in the corresponding conditions that result from alpha-globin gene deletions. In studies designed to examine this discrepancy, we have demonstrated that a significant proportion of red cells produced in an HbCS homozygote has a much reduced red cell life span. Contrary to previous reports, we have been able to demonstrate the expected deficit in alpha-chain production in this condition and have shown that both the cessation of globin chain synthesis in vitro and the destruction of the excess beta-chains occur unusually rapidly. Comparison with various deletion forms of alpha-thalassemia suggests that, in terms of intracellular globin chain precipitates and free beta-chain pool, homozygous HbCS red cells more closely resemble those of HbH disease, with three of the four alpha-genes inactivated, than they do the more comparable alpha-thalassemia carriers with only two genes deleted.

Cholecystitis associated with Enterobacter agglomerans

A case report of chronic cholecystitis due to Enterobacter agglomerans, occurred in a 54-year old female with homozygous beta-thalassemia. The patient responded successfully to cholecystectomy and sulfamethoxazole + trimetroprim therapy. The source of the infection was not known, however, cystic duct obstruction and immune deficit were thought to be the predisposing causes.

The fate of excess beta-globin chains within erythropoietic cells in alpha-thalassaemia 2 trait, alpha-thalassaemia 1 trait, haemoglobin H disease and haemoglobin Q-H disease: an electron microscope study

Electron microscope studies have been performed on bone marrow cells from individuals with various alpha-thalassaemia syndromes. Globin chain precipitates were rarely found in the erythropoietic cells of a subject with alpha-thalassaemia 2 trait. By contrast, such precipitates were found in 0.6 - 1.3% of the erythroblast and marrow reticulocyte profiles in two cases of alpha-thalassaemia 1 trait, 2.1 - 13.7% of profiles in five patients with haemoglobin H (HbH) disease and 6.2% of profiles in one patient with haemoglobin Q-H (HbQ-H) disease. In the patient with HbQ-H disease, but not in the others, the nuclei of some erythroblasts displayed the 'Swiss cheese' appearance which has been reported in some forms of congenital dyserythropoietic anaemia. It is proposed that in alpha-thalassaemia 2 trait, where the degree of excess of beta-chains is slight, most of the excess chains are degraded by proteolysis. In alpha-thalassaemia 1 trait, where there is a greater excess of beta-chains, the excess chains can undergo either proteolysis or precipitation, but there is little or no tetramerization to form soluble HbH. Finally, in HbH disease, where the degree of excess is considerable, the excess beta-chains may be subject to proteolysis, precipitation and tetramerization.

Heterogeneity of beta thalassaemia in Thailand

Beta thalassaemia in Thailand is heterogeneous. Clinical, genetical, haematological and globin chain biosynthetic studies were performed in seven beta-thalassaemia families. The results showed different gene combinations. These were alpha-thalassaemia/homozygous beta 0-thalassaemia, questionable double heterozygosity between a beta-thalassaemia and a silent beta-thalassaemia genes with low Hb F of unexplained cause, silent beta-thalassaemia/beta+ - or beta 0-thalassaemia, high Hb A2 high Hb F-beta-thalassaemia - a new mutant, mild beta+-thalassaemia/Hb E, and beta 0-thalassaemia/heterocellular HPFH or delta beta-thalassaemia associated with alpha-thalassaemia. Most of variability of clinical and haematological findings in these families is due to heterogeneity of the beta-thalassaemia and related genes.

Homozygous haemoglobin Constant Spring: a need for revision of concept

Twenty-two patients with mild haemolytic anaemia and haemoglobin (Hb) Constant Spring (CS) of around 6% were studied because they were suspected of having homozygous Hb CS. Family studies revealed Hb CS trait in both parents of eight patients, supporting that they were homozygous for Hb CS. The other patients were included because they had clinical and haematological features similar to the diagnosed cases of homozygous Hb CS. Heterozygosity and homozygosity for Hb CS are clearly distinguishable in that the former is asymptomatic but the latter is associated with overt haemolytic anaemia, and the levels of Hb CS in the two conditions of less than 1% and around 6%, respectively, do not overlap. The findings in homozygous Hb CS contradict prediction. There are four alpha-structural genes per normal human diploid genome. Hb CS trait is believed to be almost equivalent to alpha-thalassaemia 2 or a loss of one alpha-gene because HB CS, and alpha-variant, is barely or not detectable. Homozygosity for Hb CS has thus been predicted to be equivalent to alpha-thalassaemia 1 or a loss of two genes. The latter is asymptomatic and associated with microcytic-hypochromic red cells. However, Hb CS homozygosity presents with mild overt haemolytic anaemia and normal sized red cells. Pathogenesis associated with Hb CS inheritance is more complex than originally believed. There is a possibility that the unstable alpha CS mRNAs precipitate and aggregate leading to pathology of red cells and to the basophilic stippling appearance, so striking in this syndrome.

Increased circulating platelet aggregates in thalassaemia

Examination for circulating platelet aggregates according to Wu and Hoak revealed increased circulating platelet aggregates in 71% of splenectomized and 35% of nonsplenectomized patients with beta (0)-thalassaemia/Hb E disease. This may be causally related to the newly observed high incidences of pulmonary artery thrombosis and hypoxaemia in splenectomized thalassaemic patients. It is recommended that anti-platelet aggregation drugs such as aspirin and/or dipyridamole are given to thalassaemic patients after splenectomy.

Morphology and kinetics of erythropoiesis in haemoglobin H disease

Some aspects of erythroblast function have been investigated in two Thai patients with haemoglobin H disease. Electron microscope and high resolution autoradiographic studies revealed that (1) some erythroblasts and marrow reticulocytes contained branching intracytoplasmic inclusions and (2) the presence of such inclusions did not necessarily prevent the entry of cells either from the G1 phase into the S phase or from the G2 phase into mitosis. The distribution of early polychromatic erythroblasts in the different stages of the cell cycle was determined by the technique of combined Feulgen microspectrophotometry and 3H-thymidine autoradiography and found to be essentially normal. It is concluded that although the presence of an excess of alpha-chains in the beta-thalassaemia syndromes has been previously shown to be associated with a gross impairment of erythroblast proliferation, the presence of an excess beta-chains in HbH disease is not.

Ineffective erythropoiesis in haemoglobin E beta -thalassaemia: an electron microscope study

Electron microscope studies have been performed on the bone marrow cells of two non-splenectomized patients and the circulating erythroblasts and reticulocytes of three splenectomized patients with HbE/beta-thalassaemia. Some intracellular precipitates (probably consisting of alpha-chains) and mild dyserythropoietic changes were found in the early polychromatic erythroblasts within the bone marrow. Larger quantities of precipitate and more marked dyserythropoietic changes were found in the late polychromatic erythroblasts and reticulocytes both within the marrow and within the circulation. The bone marrow macrophages contained phagocytosed erythroblasts within their cytoplasm. These data indicate that the anaemia in HbE/beta-thalassaemia results largely from dyserythropoiesis and ineffective erythropoiesis. The ultrastructural abnormalities encountered in the cases of HbE/beta-thalassaemia were qualitatively and quantitatively similar to those seen in homozygous beta-thalassaemia.

Hypoxaemia and the effect of aspirin in thalassaemia

Blood gas analysis of arterial blood was performed in 34 patients with beta o-thalassaemia/haemoglobin E disease and homozygous beta o-thalassaemia. Among the 22 splenectomised patients 19 had PaO2 lower than the normal expected value, and 18 of these had PaO2 lower than 80 mmHg. Of the 12 non-splenectomised patients 5 had PaO2 lower than the expected normal value but only in one case it was lower than 80 mmHg. After aspirin or Persantin administration there was a definite rise in the PaO2 in 10 out of 12 patients. The hypoxaemia is believed to occur from increased platelet aggregation leading to pulmonary artery occlusion. The rise of the arterial PaO2 after aspirin administration indicates that the observed hypoxaemia is due to reversible platelet aggregation in the majority of cases.

Pulmonary artery obstruction in thalassaemia

A new feature has been encountered in review of a large species of autopsy materials of beta-thalassaemia/Hb E disease. Among 43 patients pulmonary arterial obstructive lesions were found in 19 (44%), of which 17 were splenectomised cases. The pulmonary arterial thromboembolism may have been due to circulating platelet aggregates. This newly discovered pathology may be an additional factor contributing toward dyspnoea and heart failure in thalassaemia besides anaemia and cardiac iron deposition. If it is proven that this pulmonary arterial thromboembolism is indeed due to circulating platelet aggregates, preventive measure by administration of drugs reducing platelet aggregation such as aspirin and Persantin may be indicated, especially after splenectomy.