Hb Lepore is a hemoglobin (Hb) variant characteri­zed by fused δ-β globin chains [1].
This variant arises by an unequal crossover that fuses the proximal end of the δ-globin gene with the distal end of a closely linked structurally homologous β-globin gene. The phenotypic expression of heterozygous Hb Lepore carriers is like a β-thalassemia (thal) trait [2,3]. Compound heterozygosity for Hb Lepore and β-thal is associated with a clinical picture like β-thal intermedia or major, depending upon the severity of the β-thal mutation [4,5]. Homozygosity for Hb Lepore results in a β-thal intermedia- or major-like phenotypic expression. Three types of Hb Lepore, that differ in the position at which the transition from δ to β DNA sequence occurs, have been described: Hb Lepore-Hollandia with a crossover between codon 22 (δ) and the 16th nucleotide (nt) of IVS-I (β) [6]; Hb Lepore-Baltimore with a crossover between codons 68 (δ) and 84 (β) [7,8]; Hb Lepore-Boston-Washington (Hb LBW) with a crossover between codon 87 (δ) and the 8th nt of IVS-II (β) [2,8].  The β-globin gene cluster is highly polymorphic [9]. A limited number of population-specific subhaplotypes, defined by restriction fragment length polymorphisms (RFLPs), have been detected [10]. Four β-globin intragenic single-base polymorphisms (at codon 2 and at IVS-II, nts 74, 81 and 666) have led to the definition of three different β-globin gene frameworks (FWs) [10]. In order to characterize the Hb Lepore genes in Hb Lepore carriers detected during the last four years in our country, we have carried out sequence analysis of their δβ breakpoint regions.