The first case of a point pathogenic variant in the RREB1 gene in Noonan-like Rasopathy.

The RREB1 is a zinc finger transcription factor that plays a role in regulating gene expression and inactivating MAPK signalling components. To date, no pathogenic variant in the RREB1 gene has been associated with any disease, but several cases of 6p terminal deletions affecting the RREB1 gene have been reported. In this study, we report the first case of RREB1-associated Noonan-like RASopathy caused by a pathogenic variant within this gene. Genetic testing included whole-genome sequencing (WGS) of the proband and Sanger sequencing of the proband, his parents, and his sibling. The proband had a de novo c.2677del, p.(Ala893Argfs*20) variant, likely resulting in RREB1 haploinsufficiency. Comparative analysis of patients with microdeletions, including in the RREB1 gene, confirmed shared clinical traits while highlighting unique features, such as blue sclerae and absence of cardiac anomalies. This study reinforces previous data on RREB1 haploinsufficiency as the driver of a new Noonan-like RASopathy variant, which includes intellectual disability, delayed motor skills, short stature, short neck, and distinctive facial dysmorphisms as key clinical indicators. These findings shed light on this RREB1-related syndrome and underscore the necessity for further investigation into the functional consequences of RREB1 mutations.