title: Double supernumerary isodicentric chromosomes derived from 15 resulting in partial hexasomy.
abstract: We report two unrelated patients each with two supernumerary marker chromosomes (SMCs) derived from chromosome 15, and thus resulting in partial hexasomy. Hexasomy in the one case (family 1) was diagnosed at prenatal diagnosis and did not include the Prader-Willi/Angelman critical region (PWACR). The double SMCs were also found in the mother, the pregnancy continued to term, and an apparently phenotypically normal child was born. This represents the first report of transmission of double SMCs from mother to child. In the second case (family 2), the hexasomy did include the PWACR and was de novo in origin. This patient manifested severe psychomotor retardation, clefting of the soft palate, hypotonia, seizure-like episodes, and other phenotypic features. The aberrant phenotype is attributable to the hexasomy for the PWACR gene loci. The normal homologs of chromosome 15 proved to be biparental in origin while the two SMCs appeared maternal.
authors.affiliation: Department of Genetics, Yale University School of Medicine, New Haven, Connecticut, USA. mazin.qumsiyeh@yale.edu
authors.forename: Mazin B
authors.initials: MB
authors.lastname: Qumsiyeh
authors.forename: Syed K
authors.initials: SK
authors.lastname: Rafi
authors.forename: Catherine
authors.initials: C
authors.lastname: Sarri
authors.forename: Maria
authors.initials: M
authors.lastname: Grigoriadou
authors.forename: Jolanda
authors.initials: J
authors.lastname: Gyftodimou
authors.forename: Effie
authors.initials: E
authors.lastname: Pandelia
authors.forename: Hara
authors.initials: H
authors.lastname: Laskari
authors.forename: Michael B
authors.initials: MB
authors.lastname: Petersen
mesh_terms: D000328:Adult; D017204:Angelman Syndrome / Q000235:genetics*; D002869:Chromosome Aberrations; D025063:Chromosome Disorders; D002884:Chromosomes, Human, Pair 15; D005260:Female; D020440:Gene Duplication; D015321:Gene Rearrangement; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D011218:Prader-Willi Syndrome / Q000235:genetics