Williams Syndrome
Overview
Plain-Language Overview
Williams Syndrome is a rare genetic condition that affects many parts of the body, especially the heart and blood vessels. It is caused by a missing piece of genetic material on chromosome 7, which impacts how the body develops. People with this condition often have distinctive facial features, such as a broad forehead and a wide mouth, and may have problems with learning and development. The heart is commonly affected, with narrowing of the arteries being a major health concern. Individuals may also have a unique personality, often described as very friendly and social. Other common issues include high calcium levels in the blood and problems with connective tissue. Overall, it is a lifelong condition that requires monitoring of heart and developmental health.
Clinical Definition
Williams Syndrome is a multisystem genetic disorder caused by a microdeletion of approximately 26-28 genes on chromosome 7q11.23, including the ELN gene encoding elastin. This deletion leads to vascular abnormalities, most notably supravalvular aortic stenosis and other arterial stenoses due to elastin deficiency. The syndrome is characterized by a distinctive facial gestalt, intellectual disability with a unique cognitive profile (relative strengths in verbal short-term memory and language, weaknesses in visuospatial tasks), and a characteristic behavioral phenotype including hypersociability. Other features include hypercalcemia in infancy, connective tissue abnormalities, and endocrine dysfunction. The cardiovascular complications are the major cause of morbidity and mortality. Diagnosis is confirmed by genetic testing identifying the 7q11.23 deletion.
Inciting Event
A de novo chromosomal microdeletion event during gametogenesis or early embryogenesis initiates the syndrome.
Rarely, inherited deletions from a parent with a balanced translocation can trigger the condition.
Latency Period
Symptoms typically become apparent in early infancy with feeding difficulties and hypercalcemia.
Characteristic facial features and cardiovascular abnormalities are often recognized by early childhood.
Developmental delays and behavioral features emerge progressively over the first few years of life.
Diagnostic Delay
Diagnosis is often delayed due to variable expressivity and subtle early signs.
Misattribution of developmental delays to nonspecific causes can postpone genetic testing.
Lack of awareness of the syndrome’s distinctive facial features and cardiovascular findings contributes to delay.
Clinical Presentation
Signs & Symptoms
Mild to moderate intellectual disability with strong verbal skills and sociable personality
Distinctive 'cocktail party' personality characterized by excessive friendliness and empathy
Hypercalcemia symptoms in infancy such as vomiting, irritability, and hypotonia
Cardiovascular symptoms including exertional dyspnea or fatigue from vascular stenoses
Musculoskeletal abnormalities such as joint laxity and short fingers
History of Present Illness
Infants present with feeding difficulties, failure to thrive, and episodes of hypercalcemia.
Parents report delayed developmental milestones including speech and motor skills.
Characteristic friendly and social personality with anxiety and attention deficits become evident in early childhood.
Cardiovascular symptoms such as murmurs or hypertension may be noted during routine exams.
Past Medical History
History of hypercalcemia or nephrocalcinosis in infancy is common.
Previous echocardiograms may reveal supravalvular aortic stenosis or other arterial stenoses.
No prior infections or exposures are typically relevant to the syndrome.
Family History
Most cases are sporadic with no family history of Williams syndrome.
Rare familial cases occur due to parental balanced translocations involving 7q11.23.
No association with other inherited syndromes is typical.
Physical Exam Findings
Elfin facial features including a broad forehead, short nose with a broad tip, and full cheeks
Supravalvular aortic stenosis murmur best heard at the upper right sternal border
Periorbital fullness and stellate iris pattern on eye exam
Short stature and mild growth delay
Hypercalcemia signs such as irritability or hypotonia in infants
Diagnostic Workup
Diagnostic Criteria
Diagnosis is established by identifying the characteristic clinical features including supravalvular aortic stenosis, distinctive facial features, and a typical neurocognitive profile. Confirmation requires detection of the 7q11.23 microdeletion using fluorescence in situ hybridization (FISH) or chromosomal microarray analysis. Laboratory findings such as hypercalcemia in infancy support the diagnosis but are not definitive. Echocardiography is essential to evaluate for vascular stenoses. Genetic testing remains the gold standard for confirming the diagnosis.
Pathophysiology
Key Mechanisms
A hemizygous deletion of 26-28 genes on chromosome 7q11.23 including the elastin gene (ELN) causes vascular abnormalities and connective tissue defects.
Loss of elastin leads to supravalvular aortic stenosis and arterial narrowing due to abnormal arterial wall elasticity.
Deletion of genes affecting neurodevelopment results in characteristic cognitive and behavioral phenotypes.
Abnormalities in calcium channel regulation contribute to hypercalcemia in infancy.
Deficiency of multiple genes in the deleted region causes distinctive facial features and endocrine abnormalities.
| Involvement | Details |
|---|---|
| Organs | Heart is commonly affected with supravalvular aortic stenosis and other vascular stenoses causing cardiac complications. |
Brain involvement leads to intellectual disability, developmental delay, and unique behavioral phenotype. | |
Kidneys may be affected by hypertension secondary to vascular abnormalities. | |
| Tissues | Arterial wall tissue is affected by elastin deficiency leading to supravalvular aortic stenosis and other vascular abnormalities. |
Connective tissue abnormalities contribute to characteristic facial features and joint laxity. | |
| Cells | Vascular smooth muscle cells contribute to the characteristic arterial stenosis due to abnormal elastin synthesis. |
Neurons are involved in the neurodevelopmental phenotype including intellectual disability and hypersociability. | |
| Chemical Mediators | Elastin deficiency due to deletion of the ELN gene causes arterial wall abnormalities and vascular stenosis. |
Matrix metalloproteinases may be involved in extracellular matrix remodeling contributing to vascular pathology. |
Treatments
Pharmacological Treatments
Antihypertensives (e.g., ACE inhibitors, calcium channel blockers)
- Mechanism:
Lower blood pressure by inhibiting the renin-angiotensin system or blocking calcium influx in vascular smooth muscle.
- Side effects:
Hypotension
Cough (ACE inhibitors)
Peripheral edema (calcium channel blockers)
- Clinical role:
First-line
Statins
- Mechanism:
Inhibit HMG-CoA reductase to reduce cholesterol synthesis and manage hyperlipidemia.
- Side effects:
Myopathy
Elevated liver enzymes
- Clinical role:
Adjunctive
Non-pharmacological Treatments
Regular cardiovascular monitoring including echocardiography to assess for supravalvular aortic stenosis and other vascular abnormalities.
Early intervention with surgical repair for significant vascular stenosis to prevent complications.
Speech and occupational therapy to address developmental delays and cognitive deficits.
Nutritional support and growth monitoring to manage feeding difficulties and failure to thrive.
Prevention
Pharmacological Prevention
Calcium and vitamin D restriction to prevent hypercalcemia in infancy
Antihypertensive therapy to manage vascular stenosis-induced hypertension
Beta-blockers or vasodilators to reduce cardiac workload in supravalvular aortic stenosis
Psychotropic medications for behavioral symptoms when indicated
Supplemental therapies such as speech and occupational therapy medications as needed
Non-pharmacological Prevention
Regular cardiovascular monitoring with echocardiography to detect progression of stenosis
Early developmental interventions including speech and occupational therapy
Nutritional counseling to manage calcium intake and feeding difficulties
Genetic counseling for families regarding recurrence risk
Audiologic screening to identify and manage hyperacusis early
Outcome & Complications
Complications
Progressive cardiovascular disease including worsening supravalvular aortic stenosis and hypertension
Sudden cardiac death due to coronary artery involvement or arrhythmias
Severe hypercalcemia causing nephrocalcinosis or renal impairment
Behavioral problems including anxiety and attention deficits
Chronic kidney disease secondary to vascular abnormalities
| Short-term Sequelae | Long-term Sequelae |
|---|---|
|
|
Differential Diagnoses
Williams Syndrome versus Noonan Syndrome
Williams Syndrome | Noonan Syndrome |
|---|---|
Typically sporadic deletion of chromosome 7q11.23 involving ELN gene | Autosomal dominant with mutations in genes like PTPN11 |
Supravalvular aortic stenosis due to elastin deficiency | Pulmonary valve stenosis and hypertrophic cardiomyopathy common |
Broad forehead, periorbital fullness, stellate iris pattern | Hypertelorism, downslanting palpebral fissures, low-set ears |
Mild intellectual disability with strong verbal skills and hypersociability | Mild to moderate intellectual disability with delayed motor milestones |
Williams Syndrome versus Marfan Syndrome
Williams Syndrome | Marfan Syndrome |
|---|---|
Typically sporadic deletion of chromosome 7q11.23 | Autosomal dominant mutation in FBN1 gene |
Supravalvular aortic stenosis and peripheral pulmonary artery stenosis | Aortic root dilation and mitral valve prolapse common |
Short stature, broad chest, and joint hyperflexibility | Tall stature, arachnodactyly, pectus excavatum, scoliosis |
Elfin facies with full cheeks and wide mouth | Long narrow face with malar hypoplasia |
Williams Syndrome versus 22q11.2 Deletion Syndrome (DiGeorge Syndrome)
Williams Syndrome | 22q11.2 Deletion Syndrome (DiGeorge Syndrome) |
|---|---|
Microdeletion on chromosome 7q11.23 | Microdeletion on chromosome 22q11.2 |
Supravalvular aortic stenosis and peripheral pulmonary artery stenosis | Conotruncal defects such as tetralogy of Fallot and interrupted aortic arch |
No primary immunodeficiency | Thymic hypoplasia causing T-cell deficiency |
Broad forehead, periorbital fullness, and stellate iris pattern | Prominent nasal root, small mouth, and hooded eyelids |
Williams Syndrome versus Smith-Magenis Syndrome
Williams Syndrome | Smith-Magenis Syndrome |
|---|---|
Deletion on chromosome 7q11.23 | Deletion on chromosome 17p11.2 |
Overfriendly, highly social behavior with anxiety | Self-injurious behaviors and sleep disturbances with inverted melatonin rhythm |
Elfin facies with broad forehead and full cheeks | Broad square face, midface hypoplasia, and prognathism |
Mild intellectual disability with relatively strong verbal skills | Moderate intellectual disability with speech delay |