title: A rare non-Robertsonian translocation involving chromosomes 15 and 21.
abstract: BACKGROUND
  Robertsonian translocations (RT) are among the most common balanced structural rearrangements in humans and comprise complete chromatin fusion of the long arm of two acrocentric chromosomes. Nevertheless, non-Robertsonian translocation involving these chromosomes is a rare event.
  
  
  METHODS
  We report a de novo unbalanced translocation involving chromosomes 15 and 21. The newborn was the daughter of a 29-year-old mother and a 42-year-old father. The couple was non-consanguineous. Clinical findings led to the diagnosis of Down syndrome (DS) with severe congenital heart defects (persistent arterial duct, and complete atrioventricular septal defect), as well as low birth length and weight (< 5th and < 10th percentile, respectively, based on specific measurement curves for DS). Conventional cytogenetic analysis revealed the karyotype 46,XX,der(15)(15pter → 15q26.2::21q11.2 → 21 qter). The translocation was confirmed by means of fluorescence in situ hybridization. The parents had normal karyotypes.
  
  
  CONCLUSIONS
  Differently from RT, in our case a rare event occurred involving the distal segment of 15q and the proximal segment of 21q. Only two reports of this translocation, involving chromosomes 15 and 21 but different breakpoints, have been described so far. The association between 21q duplication and 15q deletion makes it difficult to separate the effect of each chromosome, but might also be responsible for increasing the growth retardation, as detected in our case. Cytogenetic analysis on DS patients is mandatory not only to confirm the diagnosis, but also to assess the risk of recurrence at genetic counseling, as well as to evaluate the contribution of other chromosome aberrations in the final phenotype.
authors.affiliation: Department of Genetics, Instituto de Biociências, Universidade Estadual Paulista, BotucatuSão Paulo, Brazil.
authors.forename: Marcelo Razera
authors.initials: MR
authors.lastname: Baruffi
authors.affiliation: Department of Genetics, Instituto de Biociências, Universidade Estadual Paulista, BotucatuSão Paulo, Brazil.
authors.forename: Deise Helena
authors.initials: DH
authors.lastname: Souza
authors.affiliation: Department of Genetics, Instituto de Biociências, Universidade Estadual Paulista, BotucatuSão Paulo, Brazil.
authors.forename: Rosana Aparecida Bicudo
authors.initials: RA
authors.lastname: Silva
authors.affiliation: Department of Genetics, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão PretoSão Paulo, Brazil.
authors.forename: Ester Silveira
authors.initials: ES
authors.lastname: Ramos
authors.affiliation: Department of Genetics, Instituto de Biociências, Universidade Estadual Paulista, BotucatuSão Paulo, Brazil.
authors.forename: Danilo
authors.initials: D
authors.lastname: Moretti-Ferreira
mesh_terms: D002872:Chromosome Deletion; D002884:Chromosomes, Human, Pair 15 / Q000235:genetics*; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics*; D004314:Down Syndrome / Q000175:diagnosis / Q000235:genetics*; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007231:Infant, Newborn; D014178:Translocation, Genetic / Q000235:genetics*