RESUMO
Microscopically visible copy number variations within the proximal short arm heterochromatin and proximal long arm of chromosome 9 have been described as euchromatic variants (EVs) and are derived from extensive segmental duplications (SDs) that map to both the proximal short and long arms of chromosome 9. Recently, 3-4 additional copies of an SD cassette were found in 2 families with duplication EVs of 9q13-q21. Here, we report a third family with a duplication EV of 9q13-q21.1 that was ascertained at prenatal diagnosis for advanced maternal age and found in the fetus and her phenotypically normal mother. Dual-colour fluorescence in situ hybridization with bacterial artificial chromosomes RP11-246P17 and RP11-211E19 was consistent with the EV chromosome having 1-2 additional copies of a similar SD cassette, except that the SD-boundary clone RP11-88I18 was not apparently included. It is important to distinguish the 9q13-q21.1 EVs from possible pathogenic imbalances of chromosome 9, especially at prenatal diagnosis, as these EVs have no established phenotypic or reproductive consequences. The nature of the G-dark bands in 9q13-q21 EVs is briefly discussed.
Assuntos
Centrômero/genética , Duplicação Cromossômica , Cromossomos Humanos Par 9/genética , Eucromatina/genética , Cariótipo Anormal , Instabilidade Cromossômica , Bandeamento Cromossômico , Cromossomos Artificiais Bacterianos , Feminino , Heterocromatina/genética , Humanos , Recém-Nascido , Metáfase , Fenótipo , Gravidez , Diagnóstico Pré-NatalRESUMO
MJD is the most frequent dominant ataxia and an incapacitating disorder. Onset is most frequently during the reproductive years, and genetic counseling is its only means of prevention. The causative mutation--an expansion of a (CAG)n on chromosome 14q32.1--can now be directly detected. We now report the first two cases of prenatal diagnosis (PND). The first presented as a simultaneous request for predictive testing and PND at 14 weeks of pregnancy. Owing to time constraints, we performed a full protocol of counseling with shorter inter between sessions, while psycho-social evaluation of the other parent obstetric consults were also begun. We ensured that the couple wished termination if the fetus was a carrier, to avoid a presymptomatic test for the unborn child. We were thus able to deliver test results two weeks before PND. As the fetus carried an expanded allele (77 CAGs) inherited from his father, termination was performed and the couple received counselling, psychological and social support. The second case was the fetus of a carrier-mother that was diagnosed as non-carrier, also after amniocentesis.
Assuntos
Análise Mutacional de DNA , Doença de Machado-Joseph/diagnóstico , Doença de Machado-Joseph/genética , Diagnóstico Pré-Natal/métodos , Adulto , Amniocentese , Ataxina-3 , Cromossomos Humanos Par 14 , Feminino , Aconselhamento Genético , Idade Gestacional , Humanos , Masculino , Proteínas do Tecido Nervoso/genética , Proteínas Nucleares , Linhagem , Gravidez , Proteínas RepressorasRESUMO
La agenesia dental constituye la anomalía más común del desarrollo craneofacial. El propósito de este reporte es presentar una breve revisión de literatura acerca de esta condición clínica, la cual incluye: terminología, etiología, prevalencia, síndromes y anomalías dentales asociadas; complementado con la presentación de dos casos clínicos completos. En Colombia no hay estudios suficientes que permitan concluir las causas genéticas de esta patología, por lo que se requieren mayores investigaciones al respecto.