A small supernumerary marker chromosome resulting in mosaic partial tetrasomy 4q26-q31.21 in a foetus with multiple congenital malformations

摘要

A parental diagnosis was performed for an unborn foetus of a healthy couple, who was due for ultrasound detection of multiple malformations and abnormal amniotic fluid karyotypes. For an accurate diagnosis, routine G-banding analysis and next-generation sequencing (NGS) were carried out. Finally, conventional cytogenetic analysis suggested that the foetus had a karyotype of 47,XX,+mar[52]/46, XN, meanwhile NGS also revealed a partial tetrasomy of 27.84 Mb from 4q26-q31.21 (117,385,735-145,225,759), and G-banding analysis excluded the couple to have carried the 4q26-q31.21 duplication. We have identified a de novo mosaic small supernumerary marker chromosomes (sSMC) derived from 4q26-q31.21 in a foetus with hemivertebra, polydactyly, abnormal ears, and heart and ventricular septal defect.