Truncating Variants in <scp><i>RREB1</i></scp> Cause a Novel <scp>RASopathy</scp> Syndrome of Congenital Heart Disease, Genitourinary Malformations, and Developmental Delay

The interstitial 6p microdeletion syndrome is characterized by dysmorphic facies and structural heart, kidney, brain, and musculoskeletal differences. RREB1 haploinsufficiency and consequent abnormal RAS-MAPK pathway signaling have been proposed as a driver of the disease phenotype; however, apart from a single case report, the phenotype of intragenic RREB1 variants is unknown. Here we present a cohort of 6 individuals with truncating RREB1 variants. Phenotypes include mild dysmorphisms, congenital heart disease, genitourinary malformations, dental anomalies, and developmental delay. Our data support RREB1 as a currently under-recognized cause of a RASopathy phenotype with features that overlap with Noonan, Costello, and Cardiofaciocutaneous syndromes.