First Report of a Child With a <scp>DeSanto</scp> –Shinawi Syndrome and a Polymorphous Low‐Grade Neuroepithelial Tumor of the Young

Loss-of-function variants in the WW Domain Containing Adaptor with Coiled-Coil (WAC) gene are associated with DeSanto-Shinawi syndrome (DESSH), a rare autosomal dominant neurodevelopmental disorder usually with onset characterized by global developmental delay appearing in infancy or early youth, intellectual disability, seizures, autism spectrum disorder, attention-deficit/hyperactivity disorder, hypotonia, dysmorphic features at the level of the skull and face. The protein encoded by the WAC gene links and regulates gene transcription and monoubiquitination of histone H2B to "Lys-120" (H2BK120ub1). It also acts in the regulation of cell cycle checkpoint activation in response to DNA damage, and the RING finger 20/40 (RNF20/40)/WAC complex has been proven to act as an interactor with p53. We describe a 15-year-old boy with a diagnosis of DESSH associated with a WAC variant and a polymorphous low-grade neuroepithelial tumor of the young associated with an FGFR2(ex17):INA(ex2) fusion. In addition, two germinal likely pathogenic variants have been identified in the Neurofibromin 1 (NF1) and succinate dehydrogenase complex flavoprotein subunit A (SDHA) genes. Our data suggest a possible additional role of the WAC variant in early tumor development, highlighting the importance of oncogenetic testing in patients with rare neurodevelopmental syndromes and brain tumors.