Complex Rearrangement Involving Three Chromosomes, Four Breakpoints and a 2.7-Mb Deletion in the 18q Segment Observed in a Girl with Mild Learning Difficulties

Abstract

Complex chromosomal rearrangements (CCRs) are balanced or unbalanced structural rearrangements involving 3 or more cytogenetic break events on 2 or more different chromosomes. Here, we report a 7-year-old girl referred to our unit because of mild dysmorphic facial features, mild learning difficulties together with very mild mental retardation. Standard cytogenetic banding analysis revealed a de novo CCR involving chromosomes 1, 2 and 18. Further molecular investigation with aCGH revealed a cryptic interstitial deletion of 2.7 Mb in 18q22.1, which does not elicit a significant clinical phenotype. FISH was performed to confirm both molecular and cytogenetic results.

Research Article Characterization of a complex chromosomal rearrangement in a girl with PURA syndrome

“…It has been stated that some apparently balanced translocations are in fact CCRs; some CCRs are more complex than initially expected and could often contain cryptic genomic imbalances (Lee et al, 2010;Guilherme et al, 2013;Campos et al, 2021). Kontodiou et al (2015) agreed that using chromosome banding alone is insufficient to distinguish between a balanced versus an unbalanced CCR. The application of highresolution molecular cytogenetic methods, particularly FISH and CMA, are becoming indispensable to detect cryptic imbalances inside or outside of the breakpoint regions.…”

Unusual de novo Partial Trisomy 17p12p11.2 due to Unbalanced Insertion into 5p13.1 in a Severely Affected Boy

“…It can also contribute to the copy number variation seen in some gene clusters. 1 Besides direct or indirect duplications, gain of copy numbers can also be caused by unbalanced rearrangements, such as insertions, 2 translocations, 3 complex rearrangements, 4 or small supernumerary marker chromosomes (sSMC). 5 The proximal short arm of chromosome 17 is a genetically relatively unstable region, as it is particularly rich in regionspecific low-copy repeats (LCRs) (also known as "segmental duplications").…”