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.

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.