Diagnosis

Recognition of the syndrome can be difficult, especially in young children. Not all features need to be present and the severity of individual features varies. Roughly three-quarters of children with WBS have heart problems. This can speed up recognition. If there are no serious medical problems at birth, a diagnosis may be delayed for a long time. Many babies with WS are small and light at birth with preterm features (even in full-term pregnancies). Sucking and drinking - and thus growth - are difficult. Many infants need tube feeding. The baby cries a lot and sleeps restlessly, sometimes due to excessive blood calcium levels (hypercalcaemia). Developmental delays often become noticeable after a few months. Motor skills develop slowly. Speech comes late and learning is slow. The child remains relatively small for its age. There is usually mild to moderate intellectual disability.

FISH

The doctor who diagnoses the condition (the diagnosis) is called a clinical geneticist. In doing so, this doctor first pays attention to the immediately visible and noticeable features of WBS. In addition, the clinical geneticist does research on the hereditary material. This DNA test is also called fluorescence in situ hybridisation (FISH) and is done by taking a little blood from the child. In the blood, they look for a change (a mutation) in a certain part of the hereditary material (gene). In WBS patients, a piece of the 7th chromosome is missing. There is a clinical scoring system for making the probable diagnosis of ‘Williams syndrome’; in all patients diagnosed on this basis, the FISH test has a positive result.

If there is no immediate reason for DNA testing, other forms of testing may (together) lead to the diagnosis of WBS.