Median haemoglobin concentration during pregnancy and after delivery was about 1.0 g/dl lower in homozygous alpha+ -thalassaemia than in women with a normal alpha- globin genotype (P < or = 0.001).
This has been assessed by visual examination and fluorescein angiography in 39 subjects with SS disease and homozygous alpha+ thalassaemia and in 39 age/sex matched controls with SS disease but with a normal alpha globin genotype (alpha alpha/alpha alpha).
The severity of clinical expression seems to be modulated by coexisting alpha thalassaemia: the severely affected children have a normal complement of alpha globin genes with an unusual genotype (-alpha 3.7/alpha alpha alpha 3-7), while their father, who carries the abnormal gene with minimal symptoms, has homozygous alpha+ thalassaemia (-alpha 3.7/-alpha 3.7).
The deletions in the zeta-alpha globin gene cluster in two infants with the hemoglobin Bart's hydrops fetalis syndrome (homozygous alpha thalassemia 1) have been mapped by restriction endonuclease analysis using a zeta-specific probe.
We observed the total deletion of alpha-globin genes in homozygous alpha-thalassemia (hydrops fetalis with hemoglobin Bart's) and the deletion of particular beta and beta-like sequences in cases homozygous for hereditary persistence of fetal hemoglobin and deltabeta-thalassemia.