Swetha Ramadesikan1, Caitlyn M. Colwell1, Rachel Supinger1, Jesse Hunter1, Jessica Thomas2, Elizabeth Varga1, Elaine R. Mardis1,3, Richard J. Wood2,4 and Daniel C. Koboldt1,3 1Steve and Cindy Rasmussen Institute for Genomic Medicine, Nationwide Children's Hospital, Columbus, Ohio 43205, USA; 2Department of Pediatric Colorectal & Pelvic Reconstructive Surgery, Nationwide Children's Hospital, Columbus, Ohio 43205, USA; 3Department of Pediatrics, The Ohio State University College of Medicine, Columbus, Ohio 43210, USA; 4Department of Surgery, The Ohio State University College of Medicine, Columbus, Ohio 43210, USA Corresponding author: Daniel.Koboldtnationwidechildrens.org Abstract

Anorectal malformations (ARMs) constitute a group of congenital defects of the gastrointestinal and urogenital systems. They affect males and females, with an estimated worldwide prevalence of 1 in 5000 live births. These malformations are clinically heterogeneous and can be part of a syndromic presentation (syndromic ARM) or as a nonsyndromic entity (nonsyndromic ARM). Despite the well-recognized heritability of nonsyndromic ARM, the genetic etiology in most patients is unknown. In this study, we describe three siblings with diverse congenital anomalies of the genitourinary system, anemia, delayed milestones, and skeletal anomalies. Genome sequencing identified a novel, paternally inherited heterozygous Caudal type Homeobox 2 (CDX2) variant (c.722A > G (p.Glu241Gly)), that was present in all three affected siblings. The variant identified in this family is absent from population databases and predicted to be damaging by most in silico pathogenicity tools. So far, only two other reports implicate variants in CDX2 with ARMs. Remarkably, the individuals described in these studies had similar clinical phenotypes and genetic alterations in CDX2. CDX2 encodes a transcription factor and is considered the master regulator of gastrointestinal development. This variant maps to the homeobox domain of the encoded protein, which is critical for interaction with DNA targets. Our finding provides a potential molecular diagnosis for this family's condition and supports the role of CDX2 in anorectal anomalies. It also highlights the clinical heterogeneity and variable penetrance of ARM predisposition variants, another well-documented phenomenon. Finally, it underscores the diagnostic utility of genomic profiling of ARMs to identify the genetic etiology of these defects.

Received May 19, 2023. Accepted September 12, 2023.