KdVS is rare condition that is characterized by developmental delay and mild to moderate intellectual disability. People with this disorder typically have a disposition that is described as cheerful, sociable, and cooperative. However, also behavioural problems have been described. Many children have a low muscle tone (hypotonia) resulting in feeding problems, especially in the neonatal period. Speech and language development is delayed and atypical from onset of first words. Some children with KdVS are born with structural malformations of the brain, heart, or urogenital tract. Moreover, about half have recurrent seizures (epilepsy).
An extensive description of the broad clinical spectrum of KdVS can be found in the section Professionals – Clinical characteristics