title: Three unusual but cytogenetically similar cases with up to five different cell lines involving structural and numerical abnormalities of chromosome 18.
abstract: We report two prenatal and two postnatal diagnosed cases (the latter monozygotic twins) with ring chromosomes after GTG banding. All four, de novo r(18), cases turned out to be more complex after application of high-resolution molecular cytogenetics techniques such as use of fluorescence in situ hybridization, centromeric probes, multicolor banding, and locus-specific probes for chromosome 18. All four cases are mosaics involving chromosome 18 in up to five different cell lines, including 46,r(18); 46,dr(18); 47,r(18)x2; 46,mar(18); and 45,-18. Mosaicism sharing both numerical and structural anomalies is rare, but rings often appear as mosaics due to their mitotic instability. Overall, patients with ring chromosome 18 usually share clinical features of 18q- syndrome and, less frequently, those of 18p- syndrome. High-resolution molecular cytogenetics techniques were useful in the characterization of cases with dynamic mosaicism and in establishing the relationship between loss or gain of chromosomal material and the phenotype.
authors.affiliation: Laboratório de Citogenética e Centro de Neurociência e Biologia Celular, Faculdade de Medicina da Universidade de Coimbra, Coimbra, Portugal. i_marques@hotmail.com
authors.forename: Isabel M
authors.initials: IM
authors.lastname: Carreira
authors.forename: Alexandra
authors.initials: A
authors.lastname: Mascarenhas
authors.forename: Eunice
authors.initials: E
authors.lastname: Matoso
authors.forename: Ana B
authors.initials: AB
authors.lastname: Couceiro
authors.forename: Lina
authors.initials: L
authors.lastname: Ramos
authors.forename: Andreas
authors.initials: A
authors.lastname: Dufke
authors.forename: Marie
authors.initials: M
authors.lastname: Mazauric
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Stressig
authors.forename: Nadezda
authors.initials: N
authors.lastname: Kosyakova
authors.forename: Joana B
authors.initials: JB
authors.lastname: Melo
authors.forename: Thomas
authors.initials: T
authors.lastname: Liehr
mesh_terms: D000015:Abnormalities, Multiple / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000235:genetics; D000328:Adult; D002460:Cell Line; D002869:Chromosome Aberrations; D002887:Chromosomes, Human, Pair 18; D020732:Cytogenetic Analysis; D004200:Diseases in Twins / Q000175:diagnosis* / Q000235:genetics; D005260:Female; D006801:Humans; D009030:Mosaicism; D011296:Prenatal Diagnosis / Q000379:methods*; D012303:Ring Chromosomes; D014430:Twins, Monozygotic; D014463:Ultrasonography