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

Publication/Presentation Date

8-30-2005

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.

Volume

137

Issue

2

First Page

208

Last Page

212

ISSN

1552-4825

Disciplines

Medicine and Health Sciences | Pediatrics

PubMedID

16082706

Department(s)

Department of Pediatrics

Document Type

Article

Link to Full Text

Share

COinS