Avaliação eletroforética, cromatográfica e molecular da Hb D Los Angeles no Brasil

A variante de hemoglobina (Hb) D mais comum, Hb D Los Angeles ou D Punjab, é originada de uma transversão GAA->CAA no códon 121 da globina beta; essa mutação resulta na substituição do ácido glutâmico por glutamina na proteína. É a terceira variante de hemoglobina mais freqüente da população brasileira. Como as hemoglobinas D apresentam migração similar à hemoglobina S em pH alcalino, e com a hemoglobina A em pH ácido, são necessários vários testes para o correto diagnóstico. No presente estudo objetivou-se relacionar os diferentes procedimentos laboratoriais de rotina diagnóstica, além da análise molecular, para estabelecer o perfil de Hb D Los Angeles no Brasil. Foram analisados 47 indivíduos da população brasileira com provável Hb D Los Angeles, por vários procedimentos eletroforéticos em diferentes condições de pH, além da cromatografia líquida de alta pressão, e testes moleculares para confirmação da mutação. Foram encontrados quatro tipos de combinações de hemoglobinas: 42 indivíduos portadores de hemoglobina AD Los Angeles, dois indivíduos com doença de Hb S/D Los Angeles, dois indivíduos com Hb D Los Angeles e talassemia beta e um indivíduo com Hb D Los Angeles e Hb Lepore. Os indivíduos heterozigotos para D Los Angeles são assintomáticos, entretanto, em associação com outras variantes e talassemias podem apresentar graus variáveis de manifestações clínicas. Os resultados apresentados enfatizaram a necessidade da associação de várias metodologias para a identificação da Hb D Los Angeles, além de auxiliar na elucidação de combinações raras.<br>The most common Hb D variant, the Hb D-Los Angeles, also know as Hb D-Punjab, originates through a GAA->CAA change at the 121 codon of the beta globin gene; this mutation results in the replacement of glutamic acid for glutamine in the protein. It is the third most common hemoglobin variant in the Brazilian population. This variant has electrophoretic migration in alkaline pHs similar to Hb S and identical migration to hemoglobin A in acidic pHs. Thus, several techniques are necessary for its correct diagnosis. The purpose of this work was to relate the different laboratorial techniques and molecular analyses to determine the profile of Hb D Los Angeles in Brazil. Forty-seven individuals from the Brazilian population with Hb D Los Angeles were studied. Multiple electrophoresis in several experimental conditions were carried out, in addition to high performance liquid chromatography (HPLC) and molecular analysis to confirm this mutation. Four compound heterozygotes were observed: 42 individuals heterozygous Hb AD Los Angeles, two with Hb S/D Los Angeles disease, two individuals with Hb D Los Angeles and beta-thalassemia and one with Hb D Los Angeles and Hb Lepore. The heterozygous hemoglobin D Los Angeles is asymptomatic, even though its association with other variants and thalassemias may present varying degrees of clinical manifestations. The results presented emphasize the significance of the association of different laboratorial techniques for D Los Angeles diagnosis, and help to elucidate rare combinations

Prevalence of hemoglobinopathies in school children: the importance of using confirmatory methods

The hemoglobinopathies are included among the most common genetic diseases in the world. In Brazil, hemoglobinopathies are related to the diversity of racial backgrounds and the degree of interbreeding. The study focused on the prevalence of hemoglobinopathies using conventional and confirmatory laboratory tests in children from public schools in Ribeirão Preto-SP. The study involved the participation of 427 children between six and nine years of age. Hematologic evaluation, hemoglobin electrophoresis on cellulose acetate at alkaline pH, quantification of hemoglobin fractions by high performance liquid chromatography (HPLC) and detection of -α3.7 deletion for α thalassemia by polymerase chain reaction were performed. The results of hemoglobin electrophoresis on cellulose acetate and HPLC of the children studied showed the presence of 30 children (7%) with hemoglobinopathies. Eleven children presented results indicating suspicion of S/β-thalassemia; their parents and/or siblings were evaluated and confirmed the presence of only Hb S. The analysis of deletion -α3.7to characterize α-thalassemias sampling performed on 207 participants identified 26 children (12.6%) with deletion -α3.7. Thus, 54 (12.6%) of the children studied present this genetic alteration. For the detection of α-thalassemias it is necessary to use confirmatory methods such as molecular analysis and evaluation of family members in doubtful cases to facilitate genetic counseling in families, in which deletion -α3.7 is more frequent in Brazil.</p