Nonrecurrent Triplication of 5q21.3q23.3: A Case Report and Review of the Literature

Triplications involving 5q21.3q23.3 are rare, and a phenotype has not been established. Here, we present a 4-month-old male with dysmorphic facial features and congenital cardiac malformation. Chromosomal microarray identified a pathogenic triplication of 5q21.3q23.3 with chromosome analysis showing the extra 5q material inserted into 16q. Optical genome mapping (OGM) was performed to further characterize the triplication. We compared the clinical features of our proband with previous case reports of individuals with duplications or triplications in the region to identify a phenotype. Common features appear to include short stature, developmental delays, learning difficulties, and cardiac malformations. We discuss genes in the region with a reported role in cardiac development, hypothesize that the triplication may have resulted from microhomology-mediated break-induced replication, and discuss the utility and limitations of OGM in this case. To our knowledge, this is the first reported case of a de novo triplication of 5q21.3q23.3.