HB Fannin-Lubbock-I with a single GGC>GAC mutation at beta119(GH2)Gly-->Asp in a homozygous Mexican patient.

We studied a fast-moving, abnormal hemoglobin (Hb) identified as Fannin-Lubbock-I [beta119(GH2)Gly-->Asp] in a homozygous Mexican girl. To date, homozygosity for the Hb Fannin-Lubbock-I variant has not been reported. Her parents and five other relatives were heterozygotes. The 5' beta-globin haplotype analysis showed that the mutation was associated with haplotype 2 [- + + - +]for the epsilon, (G)gamma, (A)gamma, 5' and 3 'psibeta-globin sites, and also segregated with the TGTTC haplotype, which was constructed with five polymorphic sites of the beta-globin gene [exon 1-nucleotide (nt) 6 (C>T) and IVS-II-16 (C>G), IVS-II-46 (T>C), IVS-II-74 (G>T), and IVS-II-81 (C>T). In 1994, a variant with an additional mutation at codon 111 [beta111(G13)Val-->Leu] was described in five Spanish families. This variant was termed Hb Fannin-Lubbock-II, and the question of the existence of Hb Fannin-Lubbock-I arose. However, based on our findings, we were able to confirm the existence of Hb Fannin-Lubbock-I and propose that this mutation has a different origin from the one identified in Spanish families.

Diversity of the 5' beta-globin haplotype of four beta-thalassemia mutations in the Mexican population.

beta-Globin haplotypes have been used to investigate the origin and spread of beta-globin mutations such as Hb S [beta 6(A3)Glu-->Val, GAG>GTG], Hb E [beta 26(B8)Glu-->Lys, GAG>AAG], and beta-thalassemia (beta-thal). Molecular analyses revealed the presence of 17 beta-thal mutations in the Mexican population; the most frequent of these are the nonsense codon 39 (C>T), IVS-I-1 (G>A), IVS-I-110 (G>A), and -28 (A>C). To improve our knowledge about their origin, we analyzed the 5' haplotypes by restriction fragment length polymorphism. The codon 39 mutation (n = 17) was observed with five 5' haplotypes: 1 (59%), 2 (23%), and 4, 6, and 9 (6% each). The IVS-I-1 mutation (n = 15) was found with five 5' haplotypes: 1 (73.6%), 2, 3, 5, and 11 (6.6% each), whereas the IVS-I-110 (n = 9) and -28 mutations (n = 1) were only associated with haplotype 1. In the population studied, the codon 39 and IVS-I-1 mutations show a multicentric origin, whereas the IVS-I-110 and -28 mutations have an apparent single origin. Further investigation is required for the analysis of the polymorphisms surrounding the beta-globin gene.