title: Prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome derived from ring chromosome 4.
abstract: OBJECTIVE
  To present prenatal diagnosis and molecular cytogenetic characterization of mosaicism for a small supernumerary marker chromosome (sSMC) derived from ring chromosome, or r(4) by spectral karyotyping (SKY), fluorescence in situ hybridization (FISH), and array comparative genomic hybridization (aCGH).
  
  
  RESULTS
  A 37-year-old, primigravid woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age. Amniocentesis revealed a de novo ring-shaped sSMC in 16 of 31 amniocyte colonies. The parental karyotypes were normal. Level II ultrasound findings were unremarkable. Repeated amniocentesis revealed a karyotype of 47,XX,+mar[17]/46,XX[19]. The sSMC was characterized by SKY and FISH, which showed a chromosome 4 origin of the sSMC. aCGH demonstrated a 21.7-Mb gain in the gene dosage encompassing the region of 4p12→q13.2. The sSMC was r(4)(p12q13.2). The fetal karyotype was 47,XX,+r(4)(p12q13.2)[17]/46,XX[19]. The pregnancy was subsequently terminated. The fetus postnatally manifested hypertelorism, epicanthic folds, a prominent nose, a triangular face, low-set ears, clinodactyly of the fingers, and small big toes. Postnatal cytogenetic analyses of fetal and extraembryonic tissues revealed the karyotypes of 47,XX,+r(4)[18]/46,XX[21] in cord blood, 47,XX,+r(4)[20]/48,XX,+r(4),+r(4)[1]/46,XX[9] in umbilical cord, 47,XX,+r(4)[14]/47,XX,+dic r(4)[1]/46,XX[25] in skin, 47,XX,+r(4)[15]/46,XX[25] in amnion, and 47,XX,+r(4)[12]/47,XX,+dic r(4)[1]/46,XX[2] in placenta.
  
  
  CONCLUSIONS
  SKY, FISH, and aCGH are helpful in genetic counseling of prenatally detected sSMCs by providing the immediate and thorough information on the origin and genetic component of the sSMC.
authors.affiliation: Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, Taiwan. cpc_mmh@yahoo.com
authors.forename: Chih-Ping
authors.initials: CP
authors.lastname: Chen
authors.forename: Ming
authors.initials: M
authors.lastname: Chen
authors.forename: Yi-Ning
authors.initials: YN
authors.lastname: Su
authors.forename: Fuu-Jen
authors.initials: FJ
authors.lastname: Tsai
authors.forename: Schu-Rern
authors.initials: SR
authors.lastname: Chern
authors.forename: Pei-Chen
authors.initials: PC
authors.lastname: Wu
authors.forename: Wen-Lin
authors.initials: WL
authors.lastname: Chen
authors.forename: Li-Feng
authors.initials: LF
authors.lastname: Chen
authors.forename: Chen-Wen
authors.initials: CW
authors.lastname: Pan
authors.forename: Wayseen
authors.initials: W
authors.lastname: Wang
mesh_terms: D000015:Abnormalities, Multiple; D000028:Abortion, Induced; D000328:Adult; D025063:Chromosome Disorders / Q000175:diagnosis* / Q000235:genetics*; D002894:Chromosomes, Human, Pair 4 / Q000235:genetics; D055028:Comparative Genomic Hybridization; D005260:Female; D005819:Genetic Markers; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D009030:Mosaicism; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D012303:Ring Chromosomes; D032681:Spectral Karyotyping
chemical_list: D005819:Genetic Markers