title: Identification, characterization and clinical implications of two markers detected at prenatal diagnosis.
abstract: OBJECTIVE
  Marker chromosomes are relatively rare in the general population as its identification at prenatal diagnosis. In this article, we identified and characterized two de novo supernumerary marker chromosomes in a mosaic form at prenatal diagnosis.
  
  
  METHODS
  The two cases presented were detected during prenatal diagnosis at 17 and 15 weeks of gestation. The analyses were performed due to the advanced maternal age. In both cases, parent's karyotypes were normal. The identification of the marker chromosomes was possible by FISH techniques.
  
  
  RESULTS
  One marker chromosome was derived from chromosome 5 and the other from chromosome 6. Both children are well at the moment.
  
  
  CONCLUSIONS
  The two cases described in the present paper, join to the ones already described in the literature. However these results are the first ones without any phenotypical anomalies, at least until the present. Every new characterization of marker chromosomes at prenatal diagnosis should be reported for determining a genotype-phenotype correlation, and thus be used for genetic counselling and risk evaluation.
authors.affiliation: Serviço de Genética, Centro Hospitalar de Vila Real-Peso da Régua, Av. da Noruega, Vila Real, Portugal. genetica@chvrpr.min-saude.pt
authors.forename: Rosário Pinto
authors.initials: RP
authors.lastname: Leite
authors.forename: Marta
authors.initials: M
authors.lastname: Souto
authors.forename: Berta
authors.initials: B
authors.lastname: Carvalho
authors.forename: Márcia
authors.initials: M
authors.lastname: Martins
authors.forename: Raquel
authors.initials: R
authors.lastname: Chaves
authors.forename: Angela
authors.initials: A
authors.lastname: Morais
authors.forename: Henrique
authors.initials: H
authors.lastname: Guedes-Pinto
authors.forename: Johannes
authors.initials: J
authors.lastname: Wienberg
authors.forename: Eufémia
authors.initials: E
authors.lastname: Ribeiro
mesh_terms: D000328:Adult; D000649:Amniocentesis; D000782:Aneuploidy; D002895:Chromosomes, Human, Pair 5 / Q000235:genetics*; D002896:Chromosomes, Human, Pair 6 / Q000235:genetics*; D005260:Female; D005819:Genetic Markers; D006801:Humans; D007621:Karyotyping; D009030:Mosaicism; D011247:Pregnancy; D011256:Pregnancy Outcome; D011296:Prenatal Diagnosis / Q000379:methods*
chemical_list: D005819:Genetic Markers