Novel EED mutation in patient with Weaver syndrome

Weaver syndrome is a rare condition characterized by overgrowth, macrocephaly, accelerated osseous maturation, variable intellectual disability, and characteristic facial features. Pathogenic variants in EZH2, a histone methyltransferase, have previously been identified as a cause of Weaver syndrome. However, the underlying molecular cause in many patients remains unknown. We report a patient with a clinical diagnosis of Weaver syndrome whose exome was initially non-diagnostic. Reports in the medical literature of EED associated overgrowth prompted re-analysis of the patient's original exome data. The patient was found to have a likely pathogenic variant in EED. These findings support that Weaver syndrome is a disorder with locus heterogeneity and can be due to pathogenic variants in either EZH2 or EED. This case highlights the utility of exome sequencing as a clinical diagnostic tool for novel gene discovery as well as the importance of re-examination of exome data as new information about gene-disease associations becomes available.