A familial 3q28q29 duplication induced mild intellectual disability: case presentation and literature review

The 3q29 duplication syndrome is an uncommon imbalanced chromosomal disorder with highly variable manifestations, mainly characterized by a mild mental anomaly, eye abnormalities, and developmental delay. Only a few such cases have been reported with significant phenotypic heterogeneity. Here, we reported a case with familial 3q28q29 duplication that was 8.5 Mb in length, covering all fragments from previous reports. A series of genetic detection techniques, including karyotyping, chromosomal microarray, and fluorescence in situ hybridization, demonstrated that the rearrangement, in this case, was due to a three-chromosome translocation of the paternal grandmother of the fetus. Interestingly, only mild intellectual disability in the father and slightly thick nuchal translucency (NT) in the fetus were observed. The fetus was delivered at term and showed normal developmental milestones. Our study increased the understanding of this syndrome and highlighted the necessity and importance of the rational use of multiple genetic techniques in prenatal diagnosis.