title: Cytogenetic and molecular evaluation of 241 small supernumerary marker chromosomes: cooperative study of 19 Italian laboratories.
abstract: OBJECTIVE
  We evaluated the experiences of 19 Italian laboratories concerning 241 small supernumerary marker chromosomes (sSMCs) with the aim of answering questions arising from their origin from any chromosome, their variable size and genetic content, and their impact on the carrier's phenotype.
  
  
  METHODS
  Conventional protocols were used to set up the cultures and chromosome preparations. Both commercial and homemade probes were used for the fluorescent in situ hybridization analyses.
  
  
  RESULTS
  A total of 113 of the 241 sSMCs were detected antenatally, and 128 were detected postnatally. There were 52 inherited and 172 de novo cases. Abnormal phenotype was present in 137 cases (57%), 38 of which were antenatally diagnosed. A mosaic condition was observed in 87 cases (36%). In terms of morphology, monocentric and dicentric bisatellited marker chromosomes were the most common, followed by monocentric rings and short-arm isochromosomes. The chromosomes generating the sSMCs were acrocentric in 132 cases (69%) and non-acrocentric chromosomes in 60 cases (31%); a neocentromere was hypothesized in three cases involving chromosomes 6, 8, and 15.
  
  
  CONCLUSIONS
  The presented and published data still do not allow any definite conclusions to be drawn concerning karyotype-phenotype correlations. Only concerted efforts to characterize molecularly the sSMCs associated or not with a clinical phenotype can yield results suitable for addressing karyotype-phenotype correlations in support of genetic counseling.
authors.affiliation: Department of Experimental, Environmental Medicine, University Milan-Bicocca, Monza, Italy.
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authors.forename: Ludovica Verdun
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authors.lastname: di Cantogno
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authors.lastname: Savin
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authors.lastname: Croci
authors.forename: Fabrizia
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authors.forename: Giovanna
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authors.forename: Emilio
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authors.lastname: Donti
authors.forename: Valeria
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authors.lastname: Migliori
authors.forename: Antonella
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authors.lastname: Pettinari
authors.forename: Stefania
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authors.lastname: Bonifacio
authors.forename: Claudia
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authors.lastname: Centrone
authors.forename: Francesca
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authors.lastname: Torricelli
authors.forename: Simona
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authors.forename: Paolo
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authors.forename: Paola
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authors.lastname: Granata
authors.forename: Rosario
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authors.forename: Elisabetta
authors.initials: E
authors.lastname: Lenzini
authors.forename: Lina
authors.initials: L
authors.lastname: Artifoni
authors.forename: Vanna
authors.initials: V
authors.lastname: Pecile
authors.forename: Sergio
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authors.lastname: Barlati
authors.forename: Daniela
authors.initials: D
authors.lastname: Bellotti
authors.forename: Daniele
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authors.lastname: Caufin
authors.forename: Adalgisa
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authors.lastname: Police
authors.forename: Simona
authors.initials: S
authors.lastname: Cavani
authors.forename: Giuseppe
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authors.lastname: Piombo
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authors.lastname: Pierluigi
authors.forename: Lidia
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authors.lastname: Larizza
mesh_terms: D002869:Chromosome Aberrations; D005820:Genetic Testing / Q000379:methods*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D040582:Inheritance Patterns / Q000235:genetics; D007558:Italy; D010641:Phenotype