A Paternal "Balanced" Chromosome 2 and 4 Translocation with Chromosome 21q Insertion Leading to Duplication of 2q22.1q24.1 in Two Siblings.

Complex chromosomal rearrangements (CCRs) have been described as alterations between two or more chromosomes with at least 3 breakpoints. CCRs can cause copy number variations (CNVs) resulting in developmental disorders, multiple congenital anomalies, and recurrent miscarriages. Developmental disorders are an important health problem affecting 1-3% of children. The underlying etiology can be explained by CNV analysis in 10-20% of children who have unexplained intellectual disability, developmental delay, and congenital anomalies. Here we report two siblings who were referred to us with intellectual disability, neurodevelopmental delay, happy demeanor, and craniofacial dysmorphism due to chromosome 2q22.1q24.1 duplication. Segregation analysis showed that the duplication originated from meiotic segregation of a paternal translocation between chromosomes 2 and 4 with chromosome 21q insertion. Considering that infertility is seen in many male individuals with CCRs, it is remarkable that the father does not have any fertility problems. Gain of chromosome 2q22.1q24.1 was responsible for the phenotype due to its size and presence of a gene with a probability of being triplosensitive. We corroborate the assumption that the major gene responsible for the phenotype in the 2q23.1 region is methyl-CpG-binding domain 5, MBD5.