ALPHA-THALASSEMIA IN THE POPULATION OF CYPRUS

We have determined the alpha-thalassaemia (alpha-thal) determinants in 78 patients with Hb H disease from Cyprus; 25 were Turkish Cypriots a nd 53 were Greek Cypriots. Four deletional and three non-deletional al pha-thal alleles were present; the -alpha(3.7 kb) alpha-thal-2 and the --(MED-1)alpha-thal-1 were most frequently seen; --(MED-II) and -(alp ha)(20.5) deletions occurred at considerably lower frequencies. About 15% of all chromosomes carried a non-deletional alpha-thal-2 allele; o f these the 5 nucleotide (nt) deletion at the first intervening sequen ce (IVS-I) donor splice site was present in similar to 8% of all chrom osomes. Two types of polyadenylation signal (poly A) mutations were ob served. No striking frequency differences were seen between Greek and Turkish Cypriot patients. Combinations of the various types of alpha-t hal resulted in eight different forms of Hb H disease. The phenotypes were comparable except for great variations in the level of Hb H which was highest (average similar to 22%) in the 12 patients with the alph a(5nt)alpha/--(MED-I) combination, One patient with the same form of H b H disease but with an additional beta-thal (IVS-I-110, G --> A) hete rozygosity had a most severe microcytosis and hypochromia with < 1% Hb H. Variations in the level of Hb H might correlate with the severity of the disease, although this was not evident from the haematological data.