Phenotypic manifestations of heterozygous non-deletion alpha-thalassaemia (alpha alpha/(alpha alpha)th) in Sardinians

Alpha thalassaemia in an Italian population

The incidence of alpha-thalassaemia in an Italian population has been determined by a survey of random cord bloods for the presence of Hb Bart's. 144 out of 4730 (3%) had detectable amounts of Hb Bart's. Furthermore, alpha-globin gene analysis of 100 random cord bloods showed that five out of 100 had the common type of alpha-thalassaemia caused by a single alpha-globin gene deletion (-alpha). The molecular basis of alpha-thalassaemia was also determined in a selected group of 34 newborns with detectable levels of Hb Bart's. 25 of these cases had the -alpha 3.7 deletion type of alpha-thalassaemia and nine had nondeletion types of alpha-thalassaemia in four of which the molecular defect was detectable directly by restriction enzyme analysis.

Alpha thalassaemia in Sardinian newborns

In this study we describe the correlation between the haematological parameters (red cell indices and Hb Bart's levels) and the alpha-globin genotype in Sardinian newborns. Increased Hb Bart's levels at birth always indicates alpha-thalassaemia, either of the deletion or non-deletion variety. Infants with two alpha-globin genes deleted (- alpha/- alpha and --/ alpha alpha genotypes) had microcytosis, low MCH and Hb Bart's in the 2.0-7.1% range. A minority (38.9%) of infants with the (- alpha/ alpha alpha) globin genotype had detectable Hb Bart's, in the 0.78-2.5% range, frequently associated with minimal microcytosis while the remainder (61.1%) were completely silent. Infants carriers of a non-deletion type of alpha-thalassaemia showed Hb Bart's levels within the range found in the (- alpha / alpha alpha) genotype. The association of heterozygous beta 0-thalassemia seems to have no effect on the expression of any of these alpha-thalassaemia lesions at birth.