title: Hexasomy 13q31.3q34 due to two marker chromosomes with inverted duplication in a fetus with increased nuchal translucency.
abstract: BACKGROUND
  Small supernumerary marker chromosomes are structurally rearranged chromosomes that can be formed from different chromosomal fragments and cannot be identified using chromosomal banding analysis. Their examination has to be complemented by additional analyses like fluorescent in situ hybridization or array comparative genomic hybridization.
  
  
  METHODS
  We report on partial hexasomy of chromosome 13q in a fetus of a pregnant woman referred to genetic counseling because of increased fetal nuchal translucency and increased risk of trisomy 21 and trisomy 18 in first-trimester combined prenatal screening. Using chromosome banding analysis, in situ hybridization and array comparative hybridization we revealed the presence of two marker chromosomes with inverted duplication resulting in hexasomy of a 22.6 Mbp fragment in chromosomal region 13q31.3-13q34 with the lack of chromosome 13 centromere.
  
  
  RESULTS
  The fetus presented dysmorphic facial features, head and body disproportion, wide neck, ambiguous genitalia, incorrect position of the anus, and symmetrical shortening of the long bones were present in our described case. Some of these features were in accordance with other published cases. Other most often described features in tetrasomy were: microphtalmia or other major eye defects, ear abnormalities and deafness, hemangiomata, hypotelorism, severe learning disability and seizures. Despite a low risk of recurrence for small supernumerary marker chromosomes the possibility of germ line mosaicism exists, thus genetic counseling was offered to the examined family.
  
  
  CONCLUSIONS
  A full characterization of small supernumerary marker chromosomes in fetal karyotype is necessary for pregnancy prognosis and genetic counseling.
authors: Department of Genetics, Wroclaw Medical University, Poland.
authors: Agnieszka
authors: A
authors: Stembalska
authors: Gizela
authors: G
authors: Jagielska
authors: Izabela
authors: I
authors: Laczmanska
authors: Elzbieta
authors: E
authors: Szmida
authors: Alicja
authors: A
authors: Jarczynska
authors: Justyna
authors: J
authors: Gil
mesh_terms: D000015:Abnormalities, Multiple / Q000000981:diagnostic imaging* / Q000235:genetics; D025063:Chromosome Disorders / Q000000981:diagnostic imaging* / Q000235:genetics; D002882:Chromosomes, Human, Pair 13 / Q000235:genetics*; D005260:Female; D005333:Fetus / Q000473:pathology*; D006801:Humans; D048208:Nuchal Translucency Measurement; D011123:Polyploidy; D011247:Pregnancy; D011296:Prenatal Diagnosis
keywords: aCGH; chromosome 13; hexasomy; prenatal diagnostics; supernumerary marker chromosome