Williams syndrome

What Williams syndrome is#

Williams syndrome is a rare genetic condition marked by distinctive physical features and behaviours. These typically include a particular facial appearance, mild intellectual disability and an unusually sociable personality. The condition is caused by a missing segment, or “deletion”, of genetic material on chromosome 7.

The deletion usually happens at random. About one in every 20,000 babies is born with Williams syndrome. Males and females are equally affected, and it occurs in all populations and parts of the world.

There is currently no cure. Treatment aims to support the person and manage their symptoms.

Outlook#

The outlook depends on how severely a person is affected. In some cases, a person with Williams syndrome can finish school, work and look after themselves. Others may need lifelong care and support.

Common features#

Most people with Williams syndrome share a wide range of physical, social and cognitive (thinking and learning) traits. These features can be more or less pronounced from one person to another.

Common physical traits can include:

• distinctive facial features, such as a long upper lip, small chin, full lips, fuller cheeks, an upturned nose and a flattened nose bridge
• a squint
• low birth weight and slow weight gain; adults are usually shorter than average
• feeding difficulties in babies, including problems swallowing and very slow eating
• hyperacusis – extreme sensitivity to sound, which may include being startled by ordinary noise levels
• dental problems, such as small, oddly shaped or widely spaced teeth and a misaligned bite
• cardiovascular problems, including a narrowed aorta (aortic stenosis) and a narrowed pulmonary artery (pulmonary stenosis)
• colic or irritability in babies, which is thought to be linked to high calcium levels (hypercalcaemia)
• muscle and joint problems, including poor muscle tone, weak muscles, overly loose joints, muscle contractures and poor coordination
• higher than normal levels of calcium in the blood (hypercalcaemia)
• groin and umbilical (belly button) hernias
• kidney problems, including variations in shape and function

Intellectual and personality traits can include:

• intellectual disability, such as developmental delays
• below average IQ
• learning difficulties
• poor spatial skills
• attention deficit hyperactivity disorder (ADHD)
• an overly sociable personality – the person is often inappropriately outgoing, with little fear of strangers or social interaction

What causes Williams syndrome#

Williams syndrome is caused by the deletion of up to 28 genes on chromosome 7, meaning a section of genetic material there is missing. Some of these genes are involved in producing elastin, a protein that gives elasticity and suppleness to structures such as skin and blood vessel walls. The lack of elastin is most likely responsible for some of the distinctive physical features of the condition.

Most cases happen because of random events during the formation of the egg or the sperm in an otherwise unaffected person. Rarely, Williams syndrome can be inherited from a parent who has the condition. When it is inherited, it follows an autosomal dominant pattern, which means just one copy of the altered chromosome 7 is enough to cause it. Because of this pattern, a person with Williams syndrome has a 50 per cent chance of passing the condition on to any future children.

Williams syndrome is not linked to anything the parents did or did not do during pregnancy.

Diagnosis#

Williams syndrome often goes undiagnosed, so many people do not get the support and treatment they need until later in life. Assessment can involve reviewing the medical history and a physical examination to check for typical features.

Diagnostic tests can include:

• a blood test to check for elevated calcium levels (although high calcium is not always present)
• chromosome microarray testing, which detects Williams syndrome and many other small chromosome changes
• fluorescent in situ hybridisation (FISH), a chromosome test that checks for deletion of the elastin gene on chromosome 7

FISH testing has largely been replaced by chromosome microarray.

Treatment#

There is currently no cure for Williams syndrome, so treatment aims to support the person and manage associated symptoms. Because there may be many physical, developmental, intellectual and social issues, care often involves a team of health professionals.

Treatment options can include:

• social “training”, such as learning how to greet people appropriately rather than automatically kissing or hugging
• regular medical monitoring of the heart, blood vessels and any other physical problems that could lead to complications
• occupational therapy and physical therapy
• speech therapy
• surgery to correct heart and blood vessel problems, if needed
• dental and orthodontic treatment

Genetic counselling#

If you or a family member have been diagnosed with Williams syndrome, or if it runs in your family, it can help to speak to a genetic counsellor. Genetic counsellors are health professionals qualified in both counselling and genetics.

As well as offering emotional support, they can help you understand Williams syndrome and its causes, how it is inherited, and what a diagnosis means for your or your child’s health and development. They are trained to provide information and support that is sensitive to your family circumstances, culture and beliefs.

If the condition runs in your family, a genetic counsellor can explain the genetic testing options available to you and other relatives. You may also choose to see one if you are planning a family, to learn your chance of passing the condition on or to arrange prenatal tests.

Key points#

• Williams syndrome is caused by a missing segment (a “deletion”) of genetic material on chromosome 7.
• It is caused by the deletion of up to 28 genes, some of which help produce elastin.
• A lack of elastin is most likely responsible for some of the distinctive physical features.
• When inherited, just one copy of the altered chromosome 7 is enough to cause the condition.
• There is no cure; treatment aims to support the person and manage their symptoms.

Where to get help#