Understanding Williams Syndrome

What is Williams syndrome?   

Williams syndrome (WS) is a rare genetic disorder that occurs equally across all populations. Approximately 1 in every 7,500 individuals are born with WS. Williams syndrome is a complex disorder with highly variable presentations that involve unique medical, behavioral, and developmental features that require specialized care.  

What causes Williams syndrome? 

Williams syndrome is caused by the deletion of 25-27 genes on the 7th chromosome. This set of genes comprises the “Williams syndrome critical region,” which is the part of the chromosome formally called 7q11.23. This name tells geneticists exactly where this critical region is located. 

Genes provide our body with instructions that it uses to grow and function. A gene deletion means the body is missing a segment of genetic instructions which may lead to medical concerns. 

  • The WS deletion typically occurs spontaneously at the time of conception, with an equal chance of occurring in the egg or sperm.  

  • Because of the rarity of this spontaneous event, an individual with WS is usually the only one to have the condition in his or her family (except in cases of identical twins).  

  • However, individuals who have Williams syndrome do have a 50% chance of passing the condition to their children.  

How is Williams syndrome diagnosed? 

As infants, some individuals may have heart problems, failure to thrive, slow growth, feeding problems or other medical history that could suggest a clinical diagnosis of WS. However, genetic testing is the only way to confirm a Williams syndrome diagnosis. The most common tests used to diagnose WS are FISH (fluorescent in situ hybridization) and chromosomal microarray. 

What are common features of Williams syndrome? 

It is important to remember that there are no universal features, and every person affected by Williams syndrome is unique.  

Individuals born with Williams syndrome have a normal life expectancy but may experience medical, cognitive and behavioral challenges of varying severity. Based on current data, the systems listed below are impacted to some degree in at least half of individuals with WS. A given individual may have clinical symptoms in just a few of these systems, or many, each ranging from mild to severe presentation. 

  • Cardiovascular- Stenosis (narrowing of blood vessels), hypertension (high blood pressure)  

  • Neurodevelopmental- Developmental delays, mild to moderate intellectual disability, non-social anxiety, unique personalities 

  • Gastrointestinal- feeding difficulties, constipation, gastroesophageal reflux disease (GERD), celiac disease 

  • Musculoskeletal- differences in muscle tone (hypotonia, hypertonia) 

  • Endocrine – early puberty

Some individuals might also exhibit craniofacial, auditory, ocular, and dental differences. 

Current guidelines provided by the American Academy of Pediatrics and the Williams Syndrome Association are a great resource.