Mosaicism for Cohen-Gibson Syndrome in a Female Individual With Overgrowth and Neurodevelopmental Delay

Background

The Embryonic Ectoderm Development (EED) gene encodes a core component of the Polycomb Repressive Complex 2 (PRC2), which regulates chromatin structure and plays a key role in embryonic development and cell differentiation. Pathogenic variants in EED are associated with overgrowth-intellectual disability syndrome (Cohen-Gibson syndrome, OMIM #617561), though reported cases are rare and typically involve heterozygous germline variants. This study presents an individual with confirmed postzygotic mosaicism in EED, contributing to diagnostic complexity.