Worrawut Chinchang

Prevalence of HFE mutations among the Thai population and correlation with iron loading in haemoglobin E disorder

Abstract:  Co‐inheritance of HFE mutations has a substantial role in iron overload in β‐thalassaemia carriers in north European populations where two HFE mutations, C282Y and H63D, are prevalent. In Thailand, there was little information about the allele frequency of HFE mutations. It is of interest to determine whether such determinants represent a potential risk in developing iron overload as nearly 40% of the Thai population carry either one of thalassaemia or haemoglobinpathy alleles. A total of 380 normal controls from five different regions including Bangkok were screened for the HFE C282Y, H63D and IVS5+1 G→A alleles. In addition, 70 individuals with homozygous haemoglobin E (Hb EE) were also tested and their genotypes were correlated with levels of serum ferritin. H63D is the major HFE mutation found in the Thai population with an average allele frequency of 3% (range 1–5%). One individual was heterozygous for the splice site mutation IVS5 + 1 G → A, and the C282Y allele was not detected. In the Hb EE group, five individuals had iron deficiency (ferritin <12 μg/L) and the remaining 65 individuals had a wide range of serum ferritin levels of 16–700 μg/L. Four individuals with Hb EE were heterozygous for the H63D allele. No significant difference in serum ferritin level was detected in this group with or without the HFE mutation (137.2 ± 78 vs. 116.3 ± 128 μg/L). HFE mutations are relatively uncommon among the Thai population, and the average allele frequency of the ancient H63D mutation is similar to that of other countries in this region. Because of their paucity, it appears that these alleles are less likely to be responsible for high ferritin levels and iron loading in individuals with Hb E related disorders.

Acute haemolytic crisis in a Thai patient with homozygous haemoglobin Constant Spring (Hb CS/CS): a case report.

Abstract Acute haemolysis associated with mild upper respiratory tract infection was observed in a Thai boy who presented with a rapid decline in haemoglobin (Hb) levels, haemoglobinuria and evidence of intravascular haemolysis. Several possible causes giving rise to such a condition were excluded including G6PD deficiency, which is extremely common in Thailand. Subsequent haematological and molecular analyses demonstrated that the patient was homozygous for Hb Constant Spring (Hb CS/CS), an a globin haemoglobinopathy. It has been shown previously that patients with homozygous Hb CS had mild haemolytic anaemia secondary to an accumulation of a CS chains, which are toxic to red blood cell membrane cytoskeletons. Increased body temperature might induce more precipitation of this a globin variant. This report highlights the importance of Hb CS/CS as a potential predisposing cause of acute haemolysis in children that might be aggravated by acute bacterial or viral infections. This is particularly relevant for patients of Southeast Asian descent where this abnormal haemoglobin is highly prevalent.

Further Identification of Hb G-Coushatta [β22(B4)Glu→Ala (GAA→GCA)] in Thailand by the Polymerase Chain Reaction-Single-Strand Conformation Polymorphism Technique and by Amplification Refractory Mutation System-Polymerase Chain Reaction

Thalassemias and hemoglobinopathies are very common among Southeast Asian populations, particularly in Thailand, where it is estimated that nearly 30% of the population carries at least one such disorder. Moreover, the heterogeneity of different mutant α- and β-globin alleles contributes to the complexity in diagnosis and proper management, as more than 60 thalassemia syndromes and hemoglobinopathies have been described. Herein we report a further case of Hb G - Coushatta [β22(B4)Glu→Ala (GAA→GCA)] (also known as G - Saskatoon, G - Hsin Chu and G - Taegu) in a Thai family in which the mother was found to have an unusual hemoglobin (Hb) anomaly in combination with Hb E [β26(B8)Glu→Lys, GAG→AAG]. We applied our recently described polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique to scan the β-globin genes and found an aberrant pattern in exon 1. The molecular analysis by direct genomic sequencing successfully identified the nucleotide mutation (codon 22, GAA→GCA), and a novel amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) for this variant is described.

Identification of Hb Q-India (64 Asp→His) in Thailand

Abstract More than 30 different hemoglobin variants either affecting  or β globin chains have been identified in Thailand. The large variety in the different forms of hemoglobinopathy contributes to several complicated interactions, since different types of defective globin alleles are prevalent in Thailand and nearly 30-40% of the population are carriers of either  or β thalassemia (thal). Many rare and novel abnormal globin variants in Thai subjects have been identified in our laboratory within the past few years; including Hb Lepore-Hollandia, homozygous Hb Tak, Hb Dhonburi, Hb G-Makassar, Hb G-Coushatta, Hb New York, Hb Paksè and Hb Pak Num Po. In addition to these, here we report, for the first time, the identification of Hb Q-India, an innocuous  globin variant, in a Thai family with Indian ancestry. This report highlights the complexity associated with identifying unknown globin variants within a population that has a heterogeneous repertoire of globin chain disorders.

A Rare Association of α0-Thalassemia (– –SEA) and an Initiation Codon Mutation (ATG→A-G) of the α2 Gene Causes Hb H Disease in Thailand

Several rare and hitherto unidentified non deletional α-thalassemias (αTα or ααT) have been reported from Thailand within the past few years. Interactions of these determinants with α0-thalassemia (thal) (– –/), which is highly prevalent in this region, give rise to various genotypes (– –/αTα or – –/ααT) underlying Hb H disease. We report herein the interaction of a rare initiation codon mutation of the α2 gene and α0-thal in a Thai boy with Hb H disease. This finding highlights a wide variety of molecular pathology of the α-globin genes underlying α-thal syndrome in Southeast Asia.

Hb Woodville, a rare α-globin variant, caused by codon 6 mutation of the α1 gene

Abstract:  Since 1995, the national programme for the prevention and control of severe thalassaemia has been implemented in Thailand. This programme is composed of the population screening in pregnant women and couples by osmotic fragility, HbE screening and the confirmation test using haemoglobin analyses by electrophoresis or chromatography. Thereafter, several hitherto unidentified haemoglobins (Hbs) with structural defects are increasingly described and these variants are now easily studied using DNA technology. In this study, the authors describe the haematology and molecular analyses in a 28‐yr‐old healthy female who was identified as having an exceptionally ‘high HbA2’ from haemoglobin analysis. Subsequent analyses demonstrated that observed atypical ‘HbA2’ was, in fact, a rare innocuous α‐globin variant, called Hb Woodville [alpha 2 6(A4); Asp → Tyr]. For the first time, this abnormal Hb species is characterised at the molecular level.