A patient with mosaic partial trisomy 18 resulting from dicentric chromosome breakage

Abstract

We present a patient with minor dysmorphic features and a mosaic karyotype with two different abnormal cell lines, both involving abnormalities of chromosome 18. Twenty percent of cells studied (4/20) had 46 chromosomes with a large derivative pseudoisodicentric chromosome 18. This chromosome was deleted for 18pter and duplicated for part of proximal 18p (18p11.2 based on fluorescence in situ hybridization (FISH) studies and all of 18q. The two copies of portions of chromosome 18 were fused in an inverted fashion (duplicated for 18qter->18p11.3). The smaller der(18) was present in 80% of cells studied (16/20) and had a normal q-arm, while the p-arm was missing the subtelomere region but had duplication of a part of 18p. FISH studies showed that the larger derivative 18 contained the 18q subtelomere at each end, but the 18p subtelomere was absent, consistent with fusion of two regions within 18p resulting in deletion of the subtelomeric regions. The smaller der(18) was also missing the 18p subtelomere (with normal 18q as expected). Further testing with BAC clones mapping within 18p11.2 showed that these sequences were duplicated and inverted in both of the der(18)s. These findings lead us to hypothesize that the smaller der(18) was derived from the larger, dicentric 18 following anaphase bridge formation, with breakage distal to the duplicated segment.

Identification and characterization of a new type of asymmetrical dicentric chromosome derived from a single maternal chromosome 18

“…Both mechanisms will result in a symmetrical isodicentric chromosome. If one of the isodicentric centromeres becomes nonfunctional (inactivated), the chromosome is referred to as being either isopseudodicentric (Madan et al, 1981) or pseudoisodicentric (Morrissette et al, 2005). We report a new type of asymmetrical pseudoisodicentric chromosome derived from non-isolocal sister chromatid breaks of a parental homolog.…”

Reinforcement of tendon attachment to bioactive porous titanium by BMP‐2‐induced ectopic bone formation

“…Inverted duplications associated with terminal deletion (inv dup del) are complex rearrangements reported for an increasing number of chromosome ends [1p: Ballif et al, 2003; Tonk et al, 2005; 1q: Mewar et al, 1994; De Brasi et al, 2001; 2p: Aviram‐Goldring et al, 2000; Thangavelu et al, 2004; Gruchy et al, 2007; 2q: Bonaglia et al, 2000; 3p: Jenderny et al, 1998; Kennedy et al, 2000; 4p: Cotter et al, 2001; Kondoh et al, 2003; Beaujard et al, 2005; 4q: Van Buggenhout et al, 2004; 5p: Sreekantaiah et al, 1999; 7q: Stetten et al, 1997; 9p: Teebi et al, 1993; 10q: Hoo et al, 1995; 11p: Fisher et al, 2002; 14q: Chen et al, 2005; 15q: Genesio et al, 2004; 18p: Morrissette et al, 2005; 18q: Courtens et al, 1998; 21q: Pangalos et al, 1992; Xp: Milunsky et al, 1999; Dupont et al, 2007]. These rearrangements are more frequent than first thought based on banding techniques, as several cases were initially interpreted as terminal duplications [Bonaglia et al, 2000; De Brasi et al, 2001; Beaujard et al, 2005] or terminal deletions [Ballif et al, 2003].…”

Cryptic subtelomeric deletion plus inverted duplication at chromosome 18q in a fetus: molecular delineation by multicolor banding

“…Partial trisomy 18 has been reported extensively, but a pure form of partial trisomy 18 without involving other chromosomes is rare. Phenotypes of partial duplication of 18q resemble those of full trisomy 18 but are usually milder with longer life spans (Morrissette et al, 2005;Boghosian-Sell et al, 1994). On the other hand, partial deletions of chromosome 18, including deletion 18q, deletion 18p, ring 18, and other various forms, have an overall incidence of approximately 1 in 40,000 live births in humans (Feenstra et al, 2007).…”