Premium
A patient with mosaic partial trisomy 18 resulting from dicentric chromosome breakage
Author(s) -
Morrissette Jennifer J.D.,
Medne Livija,
Bentley Tyrone,
Owens Nancy L.,
Geiger Elizabeth,
Pipan Mary,
Zackai Elaine H.,
Shaikh Tamim,
Spinner Nancy B.
Publication year - 2005
Publication title -
american journal of medical genetics part a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.064
H-Index - 112
eISSN - 1552-4833
pISSN - 1552-4825
DOI - 10.1002/ajmg.a.30845
Subject(s) - dicentric chromosome , subtelomere , biology , chromosome 18 , isochromosome , karyotype , chromosome , genetics , derivative chromosome , gene
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. © 2005 Wiley‐Liss, Inc.