The risk of alpha-thalassaemia in offspring of beta-thalassaemia carriers in Hong Kong.
Couples in whom one is heterozygous for alpha-thalassaemia-1 and the other is heterozygous for beta-thalassaemia are assumed not to be at risk of having offspring with homozygous alpha-thalassaemia-1 or homozygous beta-thalassaemia. We retrospectively reviewed the genetic outcome of 189 pregnancies of 178 couples in whom the partners were diagnosed to be discordant heterozygotes of alpha-thalassaemia and beta-thalassaemia on haematological tests. Zeta gene mapping was performed on 158 beta-thalassaemia carriers to diagnose the presence of co-existing alpha-thalassaemia-1. Eleven patients (7 per cent) were found to be compound alpha- and beta-thalassaemia heterozygotes. They accounted for 16 pregnancies, of which five were diagnosed to be affected by homozygous alpha-thalassaemia-1. Our results show that couples presumed to be discordant heterozygotes of alpha- and beta-thalassaemia on haematological testing are at risk of having offspring with homozygous alpha-thalassaemia-1 if the zeta gene mapping of the heterozygous beta-thalassaemia partner shows co-inheritance of alpha-thalassaemia-1. Prenatal diagnosis of homozygous alpha-thalassaemia-1 should be performed on these at-risk pregnancies.
Lam
Y H
YH
Department of Obstetrics and Gynaecology, University of Hong Kong, Tsan Yuk Hospital, Hong Kong.
Ghosh
A
A
Tang
M H
MH
Chan
V
V
D002874:Chromosome Mapping; D004909:Erythrocyte Indices; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D006579:Heterozygote; D006720:Homozygote; D006723:Hong Kong; D006801:Humans; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012189:Retrospective Studies; D012307:Risk Factors; D016216:Ultrasonography, Prenatal; D017085:alpha-Thalassemia / Q000175:diagnosis / Q000235:genetics*; D017086:beta-Thalassemia / Q000235:genetics*
D006454:Hemoglobins