Abstract

FREITAS, Manuela Mota et al. Analysis of subtelomeric regions in 1180 patients with mental retardation by FISH and MLPA. Arq Med [online]. 2013, vol.27, n.1, pp.10-14. ISSN 2183-2447.

Mental retardation (MR) is a major social, educational and health problem affecting 3% of the population. Subtelomeric chromosome (RSt) aberrations are one of the major causes of MR with or without multiple abnormalities, and previous studies verified that these rearrangements contribute for 3-16% of unexplained mental retardation. between 2000-2010, in the Cytogenetic unit, Centro de Genética Médica Jacinto de Magalhães, INSA (Portugal), the subtelomeric regions from all chromosomes were ana-lysed in 1180 individuals in which the most frequent pathologies had been excluded by performing genetic studies for investigations of MR and psychomotor development delay whose karyotypes, with a minimum of 550 bands, were normal. The medical recommendation for the study included mental retardation or psychomotor development delay with or without dysmorphisms. until 2007, the analysis of metaphases, obtained from cultured lymphocytes, was performed by FISH, and after 2007, by MLPA. All the unbalanced cases detected by MLPA were confirmed by FISH. From the 1180 individuals, 60 (5.1%) showed chromosomal alterations in the subtelomeric regions. In 12 (1.0%) without familial studies, the results were considered inconclusive. In 48 abnormal cases, the parental investigation allowed us to conclude that 28 (2.4%) patients had chromosomal aberrations that might be responsible for the clinical phenotype; the remaining 20 (1.7%) were considered as polymorphisms, without pathological significance, since the apparent anomaly had been inherited from phenotypically normal parents. These results obtained in this study were compared with those already described, and they highlight the advantages/disadvantages of FISH and MLPA in the characterization of subtelomeric regions that, when modified, can cause mental retardation.

Keywords : Mental retardation; subtelomeric regions; fish (fluorescent in situ hybridization); mlpa (multiplex ligation-dependent probe amplification).

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