The -(α)(5.2) Deletion Detected in a Uruguayan Family: First Case Report in the Americas

Alpha thalassemia and alpha-MRE haplotypes in Uruguayan patients with microcytosis and hypochromia without anemia

Alpha thalassemia is the most common genetic disorder across the world, being the α-3.7 deletion the most frequent mutation. In order to analyze the spectrum and origin of alpha thalassemia mutations in Uruguay, we obtained a sample of 168 unrelated outpatients with normal hemoglobin levels with microcytosis and hypochromia from two cities: Montevideo and Salto. The presence of α-thalassemia mutations was investigated by gap-PCR, restriction endonucleases analysis and HBA2 and HBA1 genes sequencing, whereas the alpha-MRE haplotypes were investigated by sequencing. We found 55 individuals (32.7%) with α-thalassemia mutations, 51(30.4%) carrying the -α3.7 deletion, one with the -α4.2 deletion and three having the rare punctual mutation HBA2:c.-59C>T. Regarding alpha-MRE analysis, we observed a significant higher frequency of haplotype D, characteristic of African populations, in the sample with the -α3.7 deletion. These results show that α-thalassemia mutations are an important determinant of microcytosis and hypochromia in Uruguayan patients with microcytosis and hypochromia without anemia, mainly due to the -α3.7 deletion. The alpha-MRE haplotypes and the α-thalassemia mutations spectrum suggest a predominant, but not exclusive, African origin of these mutations in Uruguay.

[Identification of a new 3.8kb deletional α thalassemia and detection of the deletion fragment]

OBJECTIVE

To report the identification of a novel 3.8-kb deletion that caused α thalassemia and establish the method for detecting the deletion fragment.

METHODS

Peripheral blood samples were collected from the proband and his mother for analysis of the hematological parameters and routine test for thalassemia genes. For the sample with an inconsistency between the genotyping results and phenotypic analysis results, a specific gap-PCR was employed to identify the rare or novel mutations.

RESULTS

A novel 3814-bp deletion causing α thalassemia was found in the proband and his mother, who had genotypes of -α4.2/-α3.8 and αα/-α3.8, respectively.

CONCLUSION

We identified a 3.8-kb deletion in the α-globin gene cluster that caused α thalassemia, and this finding enriches the α thalassemia gene mutation spectrum. Specific gap-PCR offers a convenient and efficient means for for detecting this deletion fragment.