De novo heterozygous variants (i.e. only one of the two copies has a variant, and that variant is usually absent from the parents if unaffected) that affect SOX6 function are responsible for an autosomal dominant genetic disorder. Variants in SOX6 lead to core clinical features of a neurodevelopmental syndrome that included developmental delay and intellectual disability in all subjects. Inconstant features were also shared by several subjects, such as attention deficit hyperactivity disorder (11 cases), mild facial dysmorphism (9 cases), craniosynostosis (3 cases), and osteochondromas (3 cases).