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Contribuição da talassemia alfa como causa de microcitose e hipocromia em uma população brasileira

Autor Principal: Eliane Borges
Tipo: Teses/dissertações
Idioma: Português
Publicado em: 2000
Link Texto Completo: http://libdigi.unicamp.br/document/?code=vtls000215200
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Microcytosis and hypochromia, without the concomitant increase of HbA2, may be caused by a-thalassemia, sideropenia or, occasionally, chronic disease anemia.

Not rarely, individuaIs with microcytosis and hipochromia, without anemia and elevated HbA2, are detected on routine hematologic examination.

In order to investigate the contribution of a-thalassemia in these cases, 339 individuaIs (98 Blacks and 241 Caucasians), attended as outpatients at UNICAMP University Hospital, with the exception of those ftom the Clinical Hematology ambulatories, showing total Hb ~12g/dl for women and 14g/dl for men, MCV and MCH :s;80fland 27pg, respectively, and normal or decreased Hb A2(:S;3,4%),were analyzed.

Using PCR and restriction enzymes, the most common mutations causing a-thalassemia in African and Mediterranean populations (-a3.7, -a4.2, --ME,D -(a )20.5 and nondeletional aHpha , aNcola , aaNcoI and a Tsaudia forms ) were investigated, the latter for the first time among Brazilian people.

One hundred sixty nine individuals (49,9%) showed a-thalassemia: 100 Caucasians (29,5%) and 69 Blacks (20.4%).

Among Caucasians, 89 (36.9%) were -a3.7 heterozygotes (-a3.7Iaa), 6 (2.5%) homozygotes (- a3.7/-a3.7), 4 (1,7%) were heterozygous for the nondeletional aHplúa (aHplúa/aa) and 1 (0,4%) was heterozygous for --MEDdeletion (-_MEDlaa).Among Blacks, 56 (57.1%) had the - a3.7laa genotype, 12 (12.2%) the -a3.7/-a3.7genotype and 1 (1,0%) was heterozygous for aHplúa (aHplúa/aa).

These results demonstrate that, in the analyzed population, a-thalassemia is an important cause of microcytosis and hypochromia in individuaIs without anemia, contributing with about 50% ofthe cases (48% caused by the -a3.7deletion and around 2% by other mutations, such as __MEDand a,HphIa,).Although the _a,3.?deletion is known to occur at high frequencies in African descendants,its presenceamong Caucasians is probably due to the elevated degree of miscegenation of the Brazilian population.

The data obtained here are of clinical relevance, once microcytosis and hypochromia are very often interpreted asindicators of iron deficiency .