summdARY A haemoglobin survey carried out in southern Sardinian newborn infants showed an overall incidence of 12.9% with haemoglobin Bart's of more than 1%. The distribution was trimodal: low (1 to 2%), intermediate (2 to 10%), and high (about 25%). A considerable overlap was seen between the first two groups. Both the 1 to 2% and 2 to 10% groups had thalassaemia-like red cell indices at birth. Newborn infants ascertained as having ac-thalassaemia at follow-up did not necessarily have unbalanced a/non-a chain synthesis at birth. At follow-up examination two subjects in the 25% group had developed haemoglobin H disease, and the 2 to 10% group had thalassaemia-like red cell indices and unbalanced globin chain synthesis ratios indicative of hetero-zygous ac-thalassaemia. The 1 to 2% group either had normal or slightly reduced a.-chain synthesis ratios, indicative of the silent oc-thalassaemia carrier state. Two subjects with 2.0% and 2.5% haemoglobin Bart's at birth had heterozygous ,-thalassaemia at follow-up. Therefore, they were double heterozygotes for ac-and r-thalassaemia with ac/3-globin chain synthesis ratios of 0.81 and 0.86. Genotype assessment in a few families showed that infants with haemoglobin Bart's levels of more than 2% may have one of the genotypes a /-ac or-/ aoac. The ac-thalassaemias (ac-thal) are a group of genetic disorders resulting from defective a-chain synthesis, which occur in many populations including Chinese, Thai, Italian, and Negro.1-In Asian populations four ac-thalassaemia syndromes of increasing clinical severity have been recognised2: (1) the silent carrier state (a-thal 2) with no clinical manifestation and 1 to 2% Hb Bart's at birth; (2) heterozygous ac-thalassaemia (oc-thal 1), characterised by thalassaemia-like red cell indices and 5 to 6% Hb Bart's at birth; (3) Hb H disease, with haemolytic anaemia and 25 to 30 % Hb Bart's at birth; and (4) homozygous oc-thalassaemia which manifests as hydrops fetalis. These four syndromes depend on the deletion of from one to all four copies of the ac-globin structural genes (-ac/a;-/ocac;-f-ac;-/-)A1' In Mediterranean populations a-thalassaemia is relativoly common and Hb H disease is frequently found, but hydrops fetalis is rare.12 13 Information on the genetics and incidence of a-thalassaemia in Sardinia is scarce. A 6 9 % carrier rate was recently found in a thalassaemia screening programme directed at the adult population.5 Hb H disease was frequently observed14 and this may be the result of a deletion defect (-/-a) or a combination of a deletion and non-deletion defect (cacxtbal1/).15 Hydrops fetalis …


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