Balanced chromosomal rearrangements associated with intellectual disability and / or malformations are rare events but are still challenging for genetic counselling since breakpoints characterisation is not performed routinely. We used whole genome sequencing to characterise the breakpoints of chromosomal rearrangements in 55 patients with ID/M. We were able to identify the rearrangement in 49/55 patients (89%) and we provided a diagnosis for 22/49 patients (44.8%). This strategy may be used in a clinical setting and may improve the management of patients with balanced chromosomal rearrangement. (By Dr. Caroline Schluth-Bolard, https://jmg.bmj.com/content/early/2019/03/28/jmedgenet-2018-105778 )