Summary

investigated in heterozygotes and homozygotes for the sickle cell haemoglobin (Hb S). ID the heterozygotes (Hb AS) group the Hb S level showed a trimodal distribution due to presence of the normal ot-globin genes (acajaa) or of one ( — a/oar) or two ( — aj — a) ee-geoes deletions. The haematological analytes inversely correlated with the associated ar-thalassaemia (ar-thal.) genes. In the Hb S homozygotes (Hb SS), associated o-thalassaemia was found to ameliorate the clinical manifestations and improved the haematological values. Co-existing triple ar-gene arrangement, oata"*"17/, with Hb AS did not influence the haematological analytes. In Hb SS, presence of aaaf^}JI resulted in a severe sickle cell anaemia (SCA) with a high severity index (>11) and with frequent crises, transfusion requirements and hospitalizations. It is suggested that reduced level of a-chain ameliorates SCA while excess of ar-globin chain production gives rise to a severe form of SCA