Molecular analysis of a thai beta-thalassaemia heterozygote with normal haemoglobin A2 level: implication for population screening.
BACKGROUND
This study aimed to characterize the molecular basis of a beta-thalassaemia heterozygote who had a normal haemoglobin A2 level.


METHODS
Using haematological and molecular analyses, the alpha- and beta-globin genotypes in a Thai woman with normal haemoglobin A2 level, who was identified in a thalassaemia and haemoglobinopathy screening programme, were examined.


RESULTS
The patient was positive for a 0.36% one-tube osmotic fragility test but negative for the dichlorophenolindophenol dye test for haemoglobin E. Haemoglobin A and A2 were observed on cellulose acetate electrophoresis with the haemoglobin A2 of 2.0%, compatible with an alpha-thalassaemia 1 carrier. Polymerase chain reaction analysis failed to detect alpha-thalassaemia 1 (South East Asian deletion). Beta-globin gene analysis detected a severe betao-thalassaemia allele with the 4 bp (-CTTT) deletion at codons 41/42. Further analysis of the alpha-globin gene identified the homozygosity of the 3.7 kb deletion alpha-thalassaemia 2.


CONCLUSIONS
The patient was found to be an unusual case: a betao-thalassaemia carrier with a low haemoglobin A2 concentration, in combination with a homozygosity for the 3.7 kb alpha-thalassaemia 2 deletion. The approach used to characterize the patient and the result obtained in this report will prove useful for population screening of thalassaemia in regions where both alpha- and beta-thalassaemias are common.
Fucharoen
Supan
S
Department of Clinical Chemistry Faculty of Associated Medical Sciences, Khon Kaen University, Thailand. supan@mail.kku.ac.th
Fucharoen
Goonnapa
G
Sanchaisuriya
Kanokwan
K
Pengjam
Yutthana
Y
D000328:Adult; D004247:DNA / Q000032:analysis; D017931:DNA Primers / Q000737:chemistry; D005260:Female; D017353:Gene Deletion; D005914:Globins / Q000235:genetics*; D006443:Hemoglobin A2 / Q000378:metabolism*; D006579:Heterozygote; D006801:Humans; D008403:Mass Screening; D008967:Molecular Biology; D016133:Polymerase Chain Reaction; D013785:Thailand; D017085:alpha-Thalassemia / Q000235:genetics; D017086:beta-Thalassemia / Q000097:blood / Q000175:diagnosis / Q000235:genetics*
D017931:DNA Primers; D005914:Globins; D004247:DNA; D006443:Hemoglobin A2