Red Cell Disorders research paper Interaction of hemoglobin E and several forms of α–thalassemia in Cambodian families
SUPAN FUCHAROEN, KANOKWAN SANCHAISURIYA, GOONNAPA FUCHAROEN, SITTHICHAI PANYASAI, ROBYN DEVENISH, LYDA LUY
Background and Objectives. This study aimed to halassemia is a heterogeneous group of hereditary describe hematologic and molecular characterization of anemias characterized by reduced or absent pro- the interaction of hemoglobin (Hb) E and several forms of Tduction of globin chains. It is very common in α-thalassemia causing complex thalassemia syndromes in South-east Asia, the region where another structural β- two Cambodian families as well as to establish a rapid globin gene variant, hemoglobin E (HbE), is also preva- polymerase chain reaction (PCR) assay for simultaneous lent.1,2 This abnormal hemoglobin results from a single detection of Hb Constant Spring (CS) and Hb Pakse’ (PS). amino acid substitution of glutamic acid to lysine, due Design and Methods. Using PCR and DNA sequencing, to a point mutation (GAG-AAG) in codon 26 of the β- the α- and β-globin genotypes were examined. Clinical globin gene. Cambodia, a small country with a popula- and hematologic data were assessed. A multiplex asym- tion of about 11.5 million, has one of the worst health metric allele-specific PCR for differential diagnosis of systems in South-east Asia. There is a significant inci- HbCS and HbPS was developed and validated. dence of microcytic hypochromic anemias, which in the Results. Eight genotypes including heterozygous HbCS, past were mostly assumed to be caused by iron defi- heterozygous HbPS, double heterozygous HbE/HbPS, dou- ble heterozygous HbE/α-thalassemia 2, triple heterozy- ciency. However, with a study based on phenotype gous HbE/α-thalassemia /HbPS, homozygous HbE/α- analysis, it soon became apparent that thalassemia and thalassemia 2, compound α-thalassemia 2/HbCS and a hemoglobinopathies are major genetic disorders in this hitherto undescribed compound HbCS/HbPS were found country.3 As for other South-east Asian countries, inter- in these two families. Genotype-phenotype relationships actions of thalassemia and hemoglobinopathies can be are discussed and successful application of a multiplex complex and confusing. Moreover, there is a high inci- PCR system for differential diagnosis of HbCS and HbPS dence of consanguineous marriages so the occurrence is described. of genetic disorders is likely to increase without prop- Interpretation and Conclusions. The interaction of sev- er diagnosis and genetic counseling. During routine eral globin gene abnormalities in Cambodian families investigation of anemias in the Siem Reap province, emphasizes the high frequencies of thalassemia and Cambodia, we encountered two families with such hemoglobinopathies. Identification of HbPS suggests that interactions. Extensive investigation, including hema- this mutation might be common and underestimated tologic and direct globin gene analysis, revealed inter- among South-east Asian populations. A simplified PCR action of Hb E with several forms of α-thalassemia assay for simultaneous detection of HbCS and HbPS would including one previously undescribed in this popula- facilitate characterization of these genotypes in both the tion, the HbPS.4 Co-segregation of HbE with different clinical setting and population screening programs in the α-thalassemia genes in these two Cambodian families region. allowed us to compare genotype-phenotype interac- tions of these complex thalassemia syndromes. A sim- Key words: hemoglobin E, hemoglobin Constant Spring, ple polymerase chain reaction (PCR) assay for differen- hemoglobin Pakse’, thalassemia syndrome, Cambodia. tial diagnosis of HbCS and HbPS is also described. Haematologica 2003; 88:1092-1098 http://www.haematologica.org/2003_10/1092.htm Design and Methods ©2003, Ferrata Storti Foundation Subjects and hematologic analysis A total of 11 EDTA-blood samples from Cambodian subjects were obtained from two unrelated families who attended the Angkor Hospital for Children, Siem Reap, Cambodia (Figures 1 and 2). Hb level and ery- From the Departments of Clinical Chemistry (SF, SP) and Clinical Microscopy throcyte indices were immediately determined at Siem (KS, GF), Faculty of Associated Medical Sciences, Centre for Research and Development in Medical Diagnostic Laboratories (SF, KS, GF, SP), Khon Kaen Reap using the Sysmex KX 21 electronic cell counter University, Khon Kaen, Thailand, Angkor Hospital for Children (RD, LL), (TOA Medical Electronics Co., Kobe, Japan). Serum fer- Cambodia. ritin level was determined using a microparticle enzyme 5 Correspondence: Dr. Supan Fucharoen, Department of Clinical Chemistry, immunoassay with the AxSYM automated system Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, (Abbott Laboratories, Abbott Park, Illinois, USA). The Thailand, 40002. E-mail: [email protected] remaining blood specimens were sent to the Faculty of
1092 haematologica/journal of hematology vol. 88(10):october 2003 Hemoglobin E and α-thalassemia in Cambodians
Figure 1. α and β – globin genotypes in the 1 2 Cambodian family 1. The arrow indicates the proband who was a compound Hb het- I erozygote for HbCS/HbPS. Hematologic data of all family members are summarized βA/βE βA/βA in Table 1. -α3.7/αPSα αα/αCSα
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βA/βA βA/βE βA/βE βA/βA βA/βA βA/βA αα/αPSα αα/αPSα αα/αPSα αα/αPSα αCSα/αPSα -α3.7/αCSα
1 2
I Figure 2. α and β – globin genotypes in the Cambodian family 2. The βA/βA βE/βE arrow indicates the proband of this family who was a triple heterozygote PS αα α3.7 αα/α α /- for HbE, HbPS and a deletional α-tha- lassemia 2. Hematologic data of the family members are summarized in Table 1.
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