Williams syndrome is a rare genetic disorder that results in hypercalcemia, cardiovascular anomalies, neurodevelopmental and/or behavioral problems, and development of distinct facial features.

The incidence of Williams syndrome is estimated to be 1:20,000, without racial, ethnic, or gender predilection.

Unequal meiotic crossover produces interstitial deletions—notably, a deletion on band 7q11.23 near the elastin gene has been found in almost every patient with Williams syndrome.