The clinical diagnosis of WS can be confirmed by blood test.  There are two tests used to confirm WS – a microarray analysis or a FISH test.  The FISH test looks specifically for deletion of elastin (the “marker gene” for WS).  The microarray detects the full length of the deletion on chromosome #7 and can determine if an individual’s deletion is the common size of 26-28 genes or a variation (either smaller or larger).  Each of the tests is highly reliable (greater than 95%).

Many individuals with Williams syndrome remain undiagnosed or are diagnosed at a relatively late age. This is of concern since individuals with Williams syndrome can have significant and possibly progressive medical problems. When the characteristics of Williams syndrome are recognized, referral to a clinical geneticist for further diagnostic evaluation is appropriate.