Haemoglobinopathies in Southeast Asia.

In Southeast Asia α-thalassaemia, β-thalassaemia, haemoglobin (Hb) E and Hb Constant Spring (CS) are prevalent. The abnormal genes in different combinations lead to over 60 different thalassaemia syndromes, making Southeast Asia the locality with the most complex thalassaemia genotypes. The four major thalassaemic diseases are Hb Bart's hydrops fetalis (homozygous α-thalassaemia 1), homozygous β-thalassaemia, β-thalassaemia/Hb E and Hb H diseases. α-Thalassaemia, most often, occurs from gene deletions whereas point mutations and small deletions or insertions in the β-globin gene sequence are the major molecular defects responsible for most β-thalassaemias. Clinical manifestations of α-thalassaemia range from asymptomatic cases with normal findings to the totally lethal Hb Bart's hydrops fetalis syndrome. Homozygosity of β-thalassaemia results in a severe thalassaemic disease while the patients with compound heterozygosity, β-thalassaemia/Hb E, present variable severity of anaemia, and some can be as severe as homozygous β-thalassaemia. Concomitant inheritance of α-thalassaemia and increased production of Hb F are responsible for mild clinical phenotypes in some patients. However, there are still some unknown factors that can modulate disease severity in both α- and β-thalassaemias. Therefore, it is possible to set a strategy for prevention and control of thalassaemia, which includes population screening for heterozygotes, genetic counselling and foetal diagnosis with selective abortion of affected pregnancies.

Prenatal diagnosis of thalassemia and hemoglobinopathies: 20 years experience at Siriraj Hospital.

Objective: To show the experience of prenatal diagnosis of Thalassemia and hemoglobinopathies in Siriraj Hospital. Methods: Hb Bart’s hydrops fetalis can be detected by DNA study from polymerase chain reaction (PCR) product in the first trimester of pregnancy either by chorionic villus sampling (CVS) or aminocentesis but in late pregnancy it can be detected unambiguous by ultrasonography at 18-20 weeks gestation, the suspected cases are confirmed by fetal blood sampling and Hb electrophoresis. Prenatal diagnosis (PND) for β-thalassemia diseases can be done at early pregnancy by direct visualization of the PCR products on electrophoresis or by dot blot analysis of amplified DNA with a set of HRP-labeled oligonucleotide probes complementary to the mutations. If the mutation is unknown. The couples have to wait for Hb analysis by HPLC or in vitro globins chain analysis from fetal blood in the second trimester. Results: The results of PND at Siriraj Hospital are summarized as Hb Bart’s Hydrops fetalis 228 cases, Homozygous Beta-Thalassemia 126 cases, and Beta Thalassemia/Hb E disease 550 cases. There are various methods of sampling namely chorionic villous sampling, amniocentesis, fetal blood sampling, ultrasound, or even combined method. There are minimal incidences of fetal loss 9 out 904 cases which comparatively give us one of the best center for prenatal diagnosis in Asia. Conclusion: Of the 904 pregnancies, the diagnosis were obtained in 891 pregnancies in which had 5 fetal loss from dead fetus in utero after fetal blood sampling in the second trimester. The other complication occurred after sampling failure.

Role of interleukin-3 and signaling pathways on beta-thalassemia/HbE erythroid progenitor cell in culture.

In order to study the role of the cytokine interleukin-3 (IL-3) and its signaling pathways in erythropoiesis of beta-thalassemia/HbE erythroid progenitor cells, CD34 positive cells were isolated from peripheral blood of patients and healthy subjects. After culturing the cells in the presence or absence of IL-3, cell viability was measured by trypan blue staining and apoptotic cells were analyzed by flow cytometry. After 7 days of culture the highest percent erythroid progenitor cell viability was obtained with cells from healthy subjects, while the lowest percentage was found in those from splenectomized beta-thalassemia/HbE. Viability of beta-thalassemia/HbE erythroid progenitor cells in the presence of IL-3 was higher than that of nonsupplemented cells. In addition, specific inhibitors of protein kinase C (Ro-318220), phospholipase C (U-73122) and Janus kinase 2 (AG-490) were used to investigate the involvement of signaling pathways in erythropoiesis. Percent apoptosis of erythroid progenitor cells from splenectomized beta-thalassemia/HbE subjects treated with RO-318220 was higher than those of nonsplenectomized beta-thalassemia/HbE and healthy subjects. Treatment with U-73122 resulted in enhanced percent apoptotic cells from normal and beta-thalassemia/HbE subjects. All these effects were independent of IL-3 treatment.

Prevention and control of thalassemia in Asia.

Thalassemia and abnormal hemoglobin are the most common inherited diseases. The only treatment readily available in most countries is regular blood transfusion and iron chelation that is recommended in severely anemic patients with iron overload. In the last 20 years there has been much progress in terms of diagnosing, preventing and managing thalassemia. This has lead to the success of prevention and control of thalassemia in many Mediterranean countries such as Cyprus, Italy and Greece. Objective: To introduce approaches that may be applied for the control of thalassemia in developing countries including Asia where thalassemias are very prevalent.