At this time the genetic work on patients with Williams Syndrome have shown some genetic material missing off the gene responsible for elastin, which is the protein that provides the blood vessels with strength and elasticity. This gene is located on chromosome 7.

Usually Williams Syndrome is an isolated condition in the family, which means only one member in the family has it. However, if this person gets married and has children there is a chance that half of this person's children could have the condition.

Genetic Diagnosis of Williams Syndrome
Chromosomal analysis is needed especially with a test called Fluorescent IN SITU Hybridization (FISH). This test detects elastin gene abnormalities in chromosome 7 in over 98% of the patients. The geneticist should be aware of what the doctor is looking for before performing the test.