Complex DNA Structural Variant on Chromosome 2 in a Pediatric Patient with Development Delay and Congenital Malformation

The 2q31 region is commonly associated with pathogenic alleles of the HOXD cluster leading to various clinical phenotypes related to skeletal development. We present a patient with short stature, tetralogy of Fallot, and multiple congenital anomalies. Initial array comparative genomic hybridization (aCGH) revealed a de novo complex genomic rearrangement (CGR) spanning 2q31 in proband characterized as a triplication (TRP)-duplication (DUP)-triplication (TRP). Subsequent analysis applying combined next-generation sequencing methodologies including whole-genome sequencing (WGS) short-reads, PacBio WGS long-reads, and optical genome mapping (OGM) indicated two additional duplications on each end of the rearrangement, consisting of DUP-TRP-DUP-TRP-DUP. This involves three breakpoint junctions, of which each were resolved down to a nucleotide level. This genomic catastrophic event includes many disease-causing genes, and analysis of each gene and its known disorders was required in order to connect genotype to phenotype in a unique CNV.