Learning Objectives
- Identify the chromosomal microdeletion responsible for Williams syndrome.
- Recognize the unique behavioral phenotype and facial features.
- Understand the role of the elastin gene in associated cardiovascular pathology.
- Differentiate hypercalcemia in Williams syndrome from other metabolic disorders.
1. Genetics
Williams syndrome is caused by a submicroscopic deletion that is often too small to be seen on a standard karyotype.
- Defect: Congenital microdeletion of the long arm (q arm) of chromosome 7.
- Critical Gene: The deleted region includes the elastin gene. Loss of elastin leads to connective tissue and vascular abnormalities throughout the body.
Activity
2. Clinical Manifestations
The presentation is a striking mix of cognitive impairment and advanced social/verbal abilities.
| Category | Clinical Findings |
|---|---|
| Appearance | Distinctive “elfin” facies: short upturned nose, long philtrum, wide mouth, and full cheeks. |
| Neuro-Psych | Intellectual disability, but with well-developed verbal skills and extreme friendliness with strangers (“cocktail party personality”). |
| Metabolic | Hypercalcemia (increased sensitivity to Vitamin D). |
3. Cardiovascular Complications
Due to the elastin deficiency, the arterial walls develop narrowing (stenosis) in several key locations:
- Supravalvular Aortic Stenosis: The most classic cardiovascular finding.
- Pulmonary Artery Stenosis: Often seen in childhood.
- Renal Artery Stenosis: Can lead to secondary hypertension.
Activity