alpha thalassemia allele in Mexican patients with HbH disease

α-Thalassemia is one of the most prevalent hemoglobin disorders in the world, in South-East Asians, the – –SEA allele is widely found in the HbH disease patients. The purpose of this work is to describe the molecular characteristics of Hemoglobin H disease in three patients from two Mexican families, as well to analyze the DNA sequence of the – –SEA allele to determine the precise site of the crossover. The –α3.7 and – –SEA alleles were identified using an established long-PCR method modified in our laboratory. The crossover site of – –SEA mutation was analyzed by DNA sequencing. The three HbH subjects showed the same genotype –α3.7/– –SEA. The -α3.7 allele has been observed in almost every racial studied group, whereas the – –SEA allele is predominant in South-East Asian countries. DNA analysis through the breakpoint sites of the – –SEA allele in both families showed the 5’ breakpoint at the third base of codon 28 in the ψα2 gene and the 3’ breakpoint within an Alu-Jo sequence, 1,328 nucleotides upstream of the 3’HVR. Therefore the size of the deletion is 19,303 nucleotides. This is the first report in which the flanking deletion sites of the – –SEA mutation have been analyzed in Mexican patients, the 5’ and 3’ ends of the deletion is well determined.