Is Williams Syndrome the Same as Down Syndrome?

Williams syndrome and Down syndrome are chromosomal disorders affecting people from birth. Williams syndrome results from a missing chromosome, while Down syndrome is caused by an extra chromosome.

What is Williams syndrome?

Williams syndrome is a genetic disorder that affects approximately 1 in 25,000 births. The syndrome is named after Dr. J.C.P. Williams, who first identified the condition. He observed common traits among children at his hospital who were receiving treatment for cardiovascular problems, such as similar facial features and an unusually friendly and outgoing personality.

Williams syndrome is also known as:

• Beuren Syndrome
• Early Hypercalcemia Syndrome with Elfin Facies
• Elfin Facies with Hypercalcemia
• Hypercalcemia-Supravalvar Aortic Stenosis
• WBS
• Williams-Beuren Syndrome
• WMS

What is Down syndrome?

Down syndrome is the most common chromosomal condition, with 1 in 700 babies diagnosed. Most people are born with 46 chromosomes, but individuals with Down syndrome have an extra copy of chromosome 21.

While there are shared physical features and behaviors, Down syndrome has three different types:

• Trisomy 21: Around 95% of individuals with Down syndrome have Trisomy 21. Each cell in their body contains three copies of chromosome 21 instead of the usual two copies.
• Translocation Down syndrome: Roughly 3% of people with Down syndrome have an additional part or whole chromosome 21 attached to a different chromosome, rather than being a separate chromosome 21.
• Mosaic Down syndrome: Approximately 2% of individuals with Down syndrome have some cells with an extra chromosome 21, while other cells have the standard two copies of the chromosome.

What are signs of Williams syndrome vs. Down syndrome?

Signs of Williams syndrome

Typical markers of Williams syndrome include:

• Facial features: Individuals with Williams syndrome often have a broad forehead, short and broad nose, full cheeks, and a wide mouth with full lips. These features are sometimes considered elfin-looking.
• Personality: People with Williams syndrome are outgoing and very interested in others. They exhibit empathy but also experience high anxiety and phobias. Attention deficit disorder (ADD) is common as well.
• Cardiovascular disease: The missing genetic code can cause narrow large blood vessels, leading to supravalvular aortic stenosis (SVAS), a form of cardiovascular disease that is prevalent in people with Williams syndrome. If left untreated, it can result in shortness of breath, high blood pressure, chest pain, and heart failure.
• Developmental concerns: Children with Williams syndrome often experience difficulties with motor skill development.

Signs of Down syndrome

Individuals with Down syndrome may exhibit similar appearances and qualities, but the conditions vary in their manifestation.

• Intellectual development: Children with Down syndrome generally have lower IQs and slower speech compared to their peers.
• Facial features: Those diagnosed with Down syndrome often have a flattened face, particularly in the nose area, and upward-slanting almond-shaped eyes. They also have smaller ears and a short neck.
• Health concerns: Half of all babies born with Down syndrome have potentially life-threatening heart defects. Additionally, Down syndrome increases the risk of developing Alzheimer’s disease earlier in life.

What are causes of Williams syndrome vs. Down syndrome?

Causes of Williams syndrome

Williams syndrome occurs when genetic code is missing from chromosome 7, which contains approximately 25 genes. This deficiency results in inadequate production of proteins like elastin, which contributes to the characteristic cardiovascular and physical traits associated with Williams syndrome.

Causes of Down syndrome

Similar to Williams syndrome, Down syndrome is caused by a chromosome disorder resulting from an extra copy of chromosome 21. While Down syndrome is generally not hereditary, one-third of children with Down syndrome have a parent who carries a translocated chromosome 21.

The mother’s age during conception is a factor in the likelihood of the baby having Down syndrome. The chance of having a baby with Down syndrome is 1 in 2,000 for mothers at age 20 and increases to 1 in 100 by age 40.

How to diagnose Williams syndrome vs. Down syndrome

Diagnosing Williams syndrome

To diagnose Williams syndrome, your doctor will inquire about signs and symptoms that resemble the condition. The diagnosis may involve:

• Physical examination to assess associated features
• Echocardiogram and electrocardiogram (ECG) to evaluate blood vessels
• DNA blood test to check for missing genes

Two tests are used to provide a confirmed diagnosis of Williams syndrome. The first is a FISH test, which detects missing chromosomes in individuals with Williams syndrome. A chromosomal microarray uses millions of markers to identify missing or additional pieces of DNA, providing a better understanding of how severely the individual will be affected physically and mentally by the condition.

Diagnosing Down syndrome

Given its prevalence, two tests are used to diagnose Down syndrome during pregnancy, enabling doctors to identify and address any heart defects present at birth.

A screening test estimates the likelihood of having a baby with Down syndrome based on factors such as age, health, and genetics. Diagnostic tests are initially conducted using the mother’s blood, followed by amniotic fluid surrounding the baby in the womb.

If the screening test during pregnancy indicates a high chance of Down syndrome, diagnostic tests are performed for confirmation. These may include:

• Chorionic villus sampling (CVS)
• Amniocentesis
• Percutaneous umbilical blood sampling (PUBS)

Treatments of Williams syndrome vs. Down syndrome

Treating Williams syndrome

While certain symptoms of Williams syndrome can affect lifespan, individuals who receive a diagnosis can lead long lives with appropriate treatment.

Treatment plans are tailored to individual symptoms and severity. Interventions may include:

• Feeding therapy for infants with feeding problems
• Physical therapy for weak muscles or developmental delays
• Special education programs for children with developmental delays
• Behavioral counseling
• Medication for attention deficit disorder or anxiety
• Surgery to address life-threatening heart deformities
• Medication or dietary adjustments for excessive blood calcium levels

Treating Down syndrome

There is no cure for Down syndrome. Early detection is crucial for improving the life expectancy of individuals with Down syndrome. Surgery may be necessary to address health concerns such as heart defects. Additional treatments include:

• Physical therapy
• Occupational therapy
• Speech therapy
• Special education

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References:

• Centers for Disease Control and Prevention: "Facts about Down Syndrome."
• Global Down Syndrome Foundation: "Congenital Heart Defects and Down Syndrome: What Parents Should Know."
• Kennedy Krieger Institute: "Genetic, Metabolic & Chromosomal Disorders."
• National Down Syndrome Society: "What is Down Syndrome?"
• National Institute on Aging: "Alzheimer’s Disease in People with Down Syndrome."
• National Organization for Rare Disorders: "Williams Syndrome."
• Stanford Medicine: "Williams Syndrome."
• St. Louis Children’s Hospital: "Williams Syndrome."