Williams syndrome

Alternative names

Williams-Beuren syndrome

Definition

Williams syndrome is a genetic disorder characterized by mild mental retardation, distinctive facial appearance, problems with calcium balance, and blood vessel disease.

Causes, incidence, and risk factors

Williams syndrome is a genetic disorder characterized by developmental delay, unusual facial appearance, narrowing of the aorta (large artery that leaves the heart) and particular cognitive and personality profiles.

It is a rare condition caused by missing genetic material on one copy of chromosome 7. The problem is usually caused by a random mutation, so parents may not have any family history of the condition. However, a person with Williams syndrome has a 50% chance of passing the disorder on to each child. It occurs in about 1 in 20,000 births.

One of the missing genes is the gene that produces elastin, a protein that gives elasticity to blood vessels and other tissues in the body. It is likely that having only one copy of this gene results in the narrowing of blood vessels seen in this condition.

Symptoms

• mild-to-moderate mental retardation
  
• short stature relative to family
  
• feeding problems including colic, reflux, vomitting (due to low muscle tone and poor gag reflex)
  
• joint laxity which may progress to stiffness as patient gets older
  
• developmental delay
  
• initially delayed speech development may turn into relative loquacious speech later and relatively strong learning by hearing
  
• distractibility
  
• learning disorders, for example poor visual-spatial abilities
  
• blood vessel narrowing including: supravalvular aortic stenosis, pulmonic stenosis, and pulmonary artery stenosis
  
• pectus excavatum (sunken chest)
  
• clinodactyly (an inward bend of the small finger)
  
• personality traits include being overtly friendly, trusting strangers, fear of loud sounds or physical contact, and an affinity for music
  

Signs and tests

• prominent lips with an open mouth
  
• flattened nasal bridge with small upturned nose
  
• epicanthal folds
  
• long philtrum (midline from upper lip margin to lower nose)