Individuals with Williams syndrome display typical facial features, including:
- prominent cheeks
- upturned nose
- wide mouth
- irregular, widely spaced teeth.
Children may have a heart problem, typically supravalvular aortic stenosis, peripheral pulmonary artery stenosis or both. These are often present at birth or develop in early childhood.
Some children develop hypercalcaemia (abnormally high levels of calcium), usually within the first two years of life but this tends to correct itself after the third year. Hypercalcaemia may cause failure to thrive, feeding problems, irritability, vomiting, constipation and kidney problems. A number of other health problems are more common in Williams syndrome. Monitoring for high blood pressure is particularly important throughout life.
Children with Williams syndrome are usually developmentally delayed, with most having moderate learning difficulties (see entry Learning Disability). They may be slow to develop language, but by school age their spoken language is usually a relative strength. They are often clumsy and have difficulties in the integration of visual-spatial information. Most children with Williams syndrome are outgoing and socially disinhibited towards adults, including strangers, but they tend to have poor relationships with other children.
Typical behaviour difficulties include overactivity, poor concentration and distractibility, excessive anxiety, attention seeking behaviours and high rates of preoccupations and obsessions. Many children are hypersensitive to particular sounds, a condition known as hyperacusis, including electrical noises (eg vacuum cleaners).
Despite their relatively good verbal and social skills, most adults with Williams syndrome are unable to live independently and require ongoing support and supervision in everyday activities.