Stable transmission of complex chromosomal rearrangements involving chromosome 1q derived from constitutional chromoanagenesis

Abstract

Background: Chromoanagenesis events encompassing chromoanasynthesis, chromoplexy, and chromothripsis are described in cancers and can result in highly complex chromosomal rearrangements derived from 'all-at-once' catastrophic cellular events. The complexity of these rearrangements and the original descriptions in cancer cells initially led to the assumption that it was an acquired anomaly. While rare, these phenomena involving chromosome 1 have been reported a few individuals in a constitutional setting. Case presentation: Here, we describe a newborn baby who was initially referred for cytogenetic testing for multiple congenital anomalies including cystic encephalomalacia, patent ductus arteriosus, inguinal hernia, and bilateral undescended testicles. Chromosome analysis was performed and revealed a derivative chromosome 1 with an 1q24-q31 segment inserted into 1q42.13 resulting in gain of 1q24-q31. Whole genome SNP microarray analysis showed a complex pattern of copy number variants with four gains and one loss involving 1q24-q31. Mate pair next-generation sequencing analysis revealed 18 chromosome breakpoints, six gains along an 1q24-q31 segment, one deletion of 1q31.3 segment and one deletion of 1q42.13 segment, which is strongly evocative of a chromoanasynthesis event for developing this complex rearrangement. Parental chromosome analyses were performed and showed the same derivative chromosome 1 in the mother. Conclusions: To our knowledge, our case is the first case with familial constitutional chromoanagenesis involving chromosome 1q24-q42. This report emphasizes the value of performing microarray and mate pair next-generation sequencing analysis for individuals with germline abnormal or complex chromosome rearrangements.