Reordenamientos cromosómicos complejos (CCRs): Presentación de un nuevo caso con 5 puntos de rotura entre los cromosomas 4 y 8.

Abstract

Complex chromosomal rearrangements (CCRs) were first defined by Pai et al. (1980) as "structural chromosomal rearrangements with at least three breakpoints and the exchange of genetic material between two or more chromosomes”. More recently, in 2003, Houge et al. redefined CCRs as "constitutional structural rearrangements involving three or more chromosomes or having more than two breakpoints”, which has become the definition more commonly used nowadays when referring to CCRs. In general, due to the intrinsic complexity involved in their formation, CCRs are rare. However, over the years, CCRs have been classified by various authors taking into account different criteria. Therefore, they may be classified according to their transmission (either “inherited” or “de novo”), the number of breakpoints involved (“four or less” and “more than four”), and their structure, for which three types can be distinguished: a) three-way exchange CCRs, b) exceptional CCRs and c) double two-way exchange CCRs. Usually the CCRs have deletions and duplications associated, which are not easily detected unless high-resolution cytogenetic analysis is applied. However, it is the application of this technique, together with the use of the latest molecular tools, such as array-CGH (array-Comparative Genomic Hybridization), that will allow the proper characterization of the possible rearrangements in each CCR. These new technologies will also reveal the genes that have been deleted or duplicated in the CCRs, so that in some cases it may be possible to postulate the mechanism of formation of the CCR and therefore to know the prognosis and/or evolution of patients with a CCR. This article describes a patient, with growth retardation, developmental delay, nystagmus, microcephaly and micrognathia, in which high-resolution G-banded chromosome analysis together with fluorescence in situ hybridisation (FISH) and molecular techniques revealed the presence of an “exceptional”, de novo CCR, with five breakpoints and two deleted regions, involving chromosomes 4 and 8. In addition, a review of the genes located in the deleted regions and their correlation with the patient’s phenotype will be presented.