Hemoglobinopathies are the most common recessive diseases worldwide but their prevalence in Uruguay has not been investigated. In this study, 397 unrelated outpatient children from the Pereira Rosell Hospital Center (CHPR), as well as 31 selected patients with microcytic anemia and 28 β-thalassemia carriers were analyzed for hemoglobinopathies by using biochemical and molecular biology methods. Parametric and non-parametric methods were used to compare the hematological indices between groups of genotypes. Of the 397 patients in the first group, approximately 1% (0.76% HbS and 0.25% β-thalassemia) had a mutation in the HBB gene and 3.3% had β-thalassemia. These mutations had a heterogeneous distribution that varied according to individual ancestry. HbS was found exclusively in individuals with declared African ancestry and had a carrier frequency of 2.2%. The frequency of α-thalassemia carriers in outpatients of European and African ancestry was 1.2% and 6.5%, respectively. In contrast, the frequency of α-thalassemia carriers in patients with microcytic anemia was 25.8%, significantly higher (p < 0.01) than that observed in the sample as a whole and in Afro-descendants and Euro-descendants. Significant differences were observed in the hematological parameters between individuals with thalassemia genotypes and those with a normal genotype. These results indicate that hemoglobinopathies are a relevant health problem in Uruguay.

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 -α 3.7 deletion, one with the -α 4.2 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 -α 3.7 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 -α 3.7 deletion. The alpha-MRE haplotypes and the α-thalassemia mutations spectrum suggest a predominant, but not exclusive, African origin of these mutations in Uruguay.

The beta-globin gene cluster haplotypes were identified in 52 and 40 chromosomes from two Afro-Uruguayan populations located in the South and North of the country, respectively. In both regions, the 5' haplotype 2 (+ - - - -), characteristic of non-African populations, was the most frequent, reflecting a strong process of admixture in Afro-Uruguayans (0.355 and 0.262, respectively). The haplotypes 3 (- - - - +) and 4 (- + - - +), characteristics of African sub-Saharan populations, present inverse frequencies in North and South: whereas in the South haplotype 3 is the second most frequent (0.232), and haplotype 4 presents a low frequency (0.019), in the North haplotype 4 is the third most frequent (0.140), and haplotype 3 only reaches an intermediate frequency (0.088). The pairwise F(ST) and the exact test of differentiation show genetic heterogeneity between both regions. Nei's genetic distance show that South and North present affinities with Bantu groups, although the North present the smallest genetic distance with the Mandenka, a Senegalese population. With respect to 3' haplotypes, haplotype I was the most frequent in both populations, followed by haplotype II, characteristic of sub-Saharan Africans. The high frequencies of haplotype III-Asian could indicate admixture with Native American populations. The differences observed between both Uruguayan regions could be explained by microevolutionary events as genetic drift, founder effects, differential admixture, and/or distinct origin of the African slaves introduced in those regions.

6-Mercaptopurine (6-MP) is a thiopurine drug widely used in childhood acute lymphoblastic leukemia (ALL) therapy. Genes such as TPMT and NUDT15 have an outstanding role in 6-MP metabolism. Mutations in both genes explain a significant portion of hematological toxicities suffered by ALL Uruguayan pediatric patients. A variable number tandem repeat in the TPMT promoter (TPMT-VNTR) has been associated with TPMT expression. This VNTR has a conservative architecture (AnBmC). To explore new causes of hematological toxicities related to ALL therapy, we genotyped the TPMT-VNTR of 130 Uruguayan pediatric patients. Additionally, individual genetic ancestry was estimated by 45 ancestry-informative markers (AIMs). Hematological toxicity was measured as the number of leukopenia events and 6-MP dose along the maintenance phase. As previously reported, we found TPMT*2 and TPMT*3C alleles were associated to TPMT-VNTR A2BC and AB2C, respectively. However, contrasting with other reports, TPMT*3A allele was found in a heterogeneous genetic background in linkage equilibrium. Patients carrying more than 5 A repeats present a significant higher number of leukopenia events among patients without TPMT and/or NUDT15 variants. Native American ancestry and the number of A repeats were significantly correlated with the number of leukopenia events. However, the correlation between Native American ancestry and the number of leukopenia events was lost when the number of A repeats was considered as covariate. This suggests that TPMT-VNTR alleles are more relevant than Native American ancestry in the hematological toxicity. Our results emphasize that TPMT-VNTR may be used as a pharmacogenetic biomarker to predict 6-MP-related hematological toxicity in ALL childhood therapy.

Introducción. La anemia en los niños es un problema de salud pública importante en nuestro país, siendo la anemia por deficiencia de hierro la más frecuente. La frecuencia de anemia en el interior del país es mayor a lo observado en Montevideo. Sin embargo, no existen datos específicos del Departamento de Salto. Objetivos. Determinar la prevalencia de anemia en niños y niñas de 6 a 48 meses que concurren a dos Centros de Atención a la Primera Infancia (CAIF) de la ciudad de Salto y analizar los factores asociados. Metodología. Se determino los niveles de hemoglobina por punción digital en 240 niños de dos CAIF, se relevaron los antecedentes perinatales del carnet del niño/a y datos de ancestralidad por medio de una encuesta a los responsables de los niños. Resultados. La prevalencia de anemia fue de 22,5% en toda la muestra, siendo levemente mayor en el CAIF2 (27,4%) que en el CAIF1(18,4%). La frecuencia de anemia es significativamente menor en los niños que tuvieron lactancia materna exclusiva hasta los 6 meses de edad, mientras que las restantes variables analizadas no presentaron asociación con la anemia. Conclusiones. La disminución observada de la frecuencia de anemia comparada con lo reportado en 2011 sugiere que las políticas de fortificación con hierro de los alimentos y de administración de hierro profiláctico a niños entre 6 y 24 meses ha sido positiva.   Adicionalmente, la menor frecuencia de anemia observada en el CAIF1 indica la importancia de la acción coordinada entre los servicios de salud y la sociedad.