title: Extensive analysis of mosaicism in a case of Turner syndrome: the experience of 287 cytogenetic laboratories. College of American Pathologists/American College of Medical Genetics Cytogenetics Resource Committee.
abstract: OBJECTIVE
  To assemble and interpret karyotype data provided as part of the College of American Pathologists/American College of Medical Genetics Cytogenetics Proficiency Testing Program.
  
  
  METHODS
  The Cytogenetics Resource Committee requested data on all cells analyzed in a 1994 whole-blood specimen challenge. In that study, 287 participating laboratories analyzed a total of 14297 cells derived from a sample drawn from an adult donor with Turner syndrome. This individual had previously been found to have mosaicism, including cell lines with X structural anomalies along with monosomy X, making this an excellent challenge for a multicenter cytogenetic survey.
  
  
  CONCLUSIONS
  Analysis of the data from this extensive study revealed mosaicism of up to 10 different sex chromosome complements involving the X chromosome with and without a small ring X or a derivative X chromosome. In the routine cytogenetic analysis performed by the participating laboratories, cell lines observed, in decreasing order of prevalence, included 45,X (n = 8357 cells), 46,X,r(X) (n = 3597), 46,X,der(X)t(X;X) (n = 2237), 46,XX (n = 93), 47,X,r(X),r(X) (n = 5), 47,X,der (X)t(X;X),der(X)t(X;X) (n = 3), 47,XX,r(X) (n = 2), and one observation each of 47,XX,der(X)t(X;X), 47,X,der(X)t (X;X),r(X), and 47,XXX. Our molecular cytogenetic data, as well as detailed analysis of G-banded chromosomes, suggest the nomenclature for these 2 abnormal X chromosomes as r(X)(p11.3q21.3) and der(X)t(X;X)(p11.3;q21.3), and we discuss models for the concomitant formation of these 2 entities. Both the degree of analysis and the extensive mosaicism that was discovered in this study are exceptional, and similar reported cases as well as possible mechanisms for the observed X chromosome instability are reviewed.
authors.affiliation: Department of Pathology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Park
authors.forename: A R
authors.initials: AR
authors.lastname: Brothman
authors.forename: M G
authors.initials: MG
authors.lastname: Butler
authors.forename: L D
authors.initials: LD
authors.lastname: Cooley
authors.forename: G W
authors.initials: GW
authors.lastname: Dewald
authors.forename: K F
authors.initials: KF
authors.lastname: Lundquist
authors.forename: C G
authors.initials: CG
authors.lastname: Palmer
authors.forename: S R
authors.initials: SR
authors.lastname: Patil
authors.forename: K W
authors.initials: KW
authors.lastname: Rao
authors.forename: I A
authors.initials: IA
authors.lastname: Saikevych
authors.forename: N R
authors.initials: NR
authors.lastname: Schneider
authors.forename: G H
authors.initials: GH
authors.lastname: Vance
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D009030:Mosaicism / Q000235:genetics*; D014424:Turner Syndrome / Q000235:genetics* / Q000473:pathology*; D014960:X Chromosome