EZH2-related overgrowth includes EZH2-related Weaver syndrome at one end of the spectrum and tall stature at the other. Although most individuals diagnosed with a heterozygous EZH2 mutation have been identified because of a clinical suspicion of Weaver syndrome, a minority have been identified through molecular genetic testing of family members of probands or individuals with overgrowth who did not have a clinical diagnosis of Weaver syndrome. Thus, the extent of the phenotypic spectrum associated with heterozygous EZH2 mutations is not yet known. Weaver syndrome is characterized by tall stature, variable intellect (ranging from normal intellect to severe intellectual disability), characteristic facial appearance, and a range of associated clinical features including advanced bone age, poor coordination, soft doughy skin, camptodactyly of the fingers or toes, umbilical hernia, abnormal tone, and hoarse low cry in infancy. Neuronal migration disorders have also been reported in a few individuals with EZH2-related overgrowth. Malignancies (including neuroblastoma and hematologic malignancies) may occur with increased frequently; current data are insufficient to draw conclusions.