EDITORCarriers of de novo balanced reciprocal translocations and inversions have an increased risk of approximately 6% for developing multiple congenital abnormalities (MCA) and/or mental retardation (MR), compared to a 2-3% risk overall in newborn populations.^1 2 Cytogenetically cryptic deletions or physical disruption or inactivation of a gene(s) in one or both breakpoint regions may account for the observed phenotypes.^3 4 It seems plausible to assume that the risk for MCA/MR may be even higher in carriers of de novo complex chromosome rearrangements (CCRs), which involve at least three different chromosomes and breakpoint regions. Extreme cases involving up to seven chromosomes and 10 breakpoints have been described.^5-7 Indeed, most reported CCRs are associated with MCA/MR.^8 9 In addition, they have been found in infertile men¹⁰ and in women suffering from multiple miscarriages.^11 12

The complex nature of CCRs renders karyotype interpretation by classical chromosome banding alone difficult. In many cases fluorescence in situ hybridisation . . . [Full text of this article]