title: Cytogenetic and molecular studies of an X;21 translocation previously diagnosed as complete monosomy 21.
abstract: We studied a child with apparent monosomy of chromosome 21. Cytogenetic, FISH and microsatellite analyses revealed a 45,X,-21,+der(X)t(X;21)(q25;q21.1) karyotype resulting from a de novo, unbalanced, X;21 non-reciprocal translocation of paternal origin, with partial monosomy of chromosomes 21 and X. An extreme, skewed X-inactivation pattern of the der(X) chromosome was demonstrated. Skewed inactivation probably accounted for a mild phenotype with respect to Xq25-->qter deletion while propagation of inactivation to the adjacent 21q region may account for mild clinical features associated to distal 21q monosomy.
authors.affiliation: Genetics Division, Instituto Nacional de Câncer, Rio de Janeiro, Brazil.
authors.forename: Leila C A
authors.initials: LC
authors.lastname: Cardoso
authors.forename: Lúcia
authors.initials: L
authors.lastname: Moraes
authors.forename: Maria Jesus E
authors.initials: MJ
authors.lastname: Camilo
authors.forename: Milene V
authors.initials: MV
authors.lastname: Mulatinho
authors.forename: Hilda
authors.initials: H
authors.lastname: Ramos
authors.forename: José Carlos C
authors.initials: JC
authors.lastname: Almeida
authors.forename: Juan C
authors.initials: JC
authors.lastname: Llerena
authors.forename: Héctor N
authors.initials: HN
authors.lastname: Seuánez
authors.forename: Fernando R
authors.initials: FR
authors.lastname: Vargas
mesh_terms: D002675:Child, Preschool; D002891:Chromosomes, Human, Pair 21; D041321:Chromosomes, Human, X; D005260:Female; D018392:Genomic Imprinting; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D009006:Monosomy; D014178:Translocation, Genetic; D049951:X Chromosome Inactivation