P476: Identification of ZMIZ1-related neurodevelopmental disorder in neonates with atrioventricular septal defects: Expansion of phenotypes and implications for counseling

Diagnostic Workup: After consent and clinical chart review, short-read genome sequencing (GS) was performed as part of the CincyKidsSeq study for Twin A using NovaSeq Plus Illumina sequencing to an average depth of 30x.Alignment against reference build 38 and variant calling were performed with Illumina DRAGEN pipeline.Variants were prioritized for review using GEM (Fabric Genomics) and classified for clinical significance based on ACMG guidelines.GS indicated homozygosity for an in-frame deletion of CYP2U1, c.367_375del p.(Gly123_Tyr125del), resulting in the loss of 3 amino acids.Targeted Sanger sequencing identified biological parents as heterozygotes, and Twin B was confirmed to be homozygous.