Abstract

GARDUNO-ZARAZUA, Luz María; GIAMMATTEO ALOIS, Lucila; KOFMAN-EPSTEIN, Susana  and  CERVANTES PEREDO, Alicia B.. Prevalence of mosaicism for trisomy 21 and cytogenetic variant analysis in patients with clinical diagnosis of Down syndrome: a 24-year review (1986-2010) at the Servicio de Genética, Hospital General de México ''Dr. Eduardo Liceaga''. Bol. Med. Hosp. Infant. Mex. [online]. 2013, vol.70, n.1, pp.31-36. ISSN 1665-1146.

Background. Down syndrome is the principal genetic cause of learning disabilities, with an incidence of 1/650 live births. Diagnosis is confirmed by karyotyping. Chromosomal variants are important for genetic counseling. We determined the prevalence of cytogenetic variants in patients with clinically diagnosed Down syndrome in the Hospital General de México Dr. Eduardo Liceaga and discussed its relevance according to maternal age. Methods. We reviewed karyotype data of patients with clinically diagnosed Down syndrome from January 1986 to December 2010 and obtained maternal and patient ages. Results. From 581 patients analyzed, 71 (12.22%) had normal karyotype. In 510 patients we confirmed that 445 (87.3%) had a regular trisomy, 22 (6.3%) were the product of a Robertsonian translocation and mosaicism was found in 43 (8.4%) patients. Maternal age was higher in patients with regular trisomy (median: 30 years) and mosaicism (median: 29 years) than in those with translocations (median: 20 years). Conclusions. Characterization of chromosomal aberrations in Mexican DS patients allows us to offer appropriate genetic counseling and to establish the prevalence of mosaicism in our population, which was higher than the reported data. Cytogenetic analysis for detection of mosaicism is important in patients with scarce clinical data of DS or with learning disabilities of unknown origin.

Keywords : Down syndrome; trisomy 21; mosaicism; chromosomal aberrations.

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