Interaction between Hb Hasharon and alpha-thalassemia: an approach to the problem of the number of human alpha loci.

We report the case of an Italian infant girl from Polesine (Po delta region in northern Italy) who was heterozygous for Hb Hasharon and alpha-thalassemia, did not synthesize any normal HbA, and had 3% HbH on electrophoresis. Hematologic and biosynthetic studies on Hb Hasharon carriers of the propositus' family suggest the possibility that the Hb Hasharon gene is linked to an alpha-thalassemia gene. On the other hand, in the Askenazy carriers of Hb Hasharon, Hb Harsharon is probably linked to a normal alpha gene. In comparing Hb Hasharon's behavior with that of other alpha variants, particularly HbG Philadelphia, frequent recombinations between alpha structural genes were suggested. The possible identity between the single alpha locus and the alpha2-thalassemia genotype is discussed.