Williams syndrome

Definition

Williams syndrome is a genetic disorder characterized by mild mental retardation

Alternative Names

Causes

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 part of the 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 25 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, vomiting (due to low muscle tone and poor gag reflex)
• joint laxity that may progress to stiffness as patient gets older
• developmental delay
• initially delayed speech development may turn into relatively loquacious speech later and relatively strong learning by hearing
• distractibility, attention deficit (ADD) 
• learning disorders, for example poor visual-spatial abilities
• blood vessel narrowing including: supravalvular aortic stenosis, pulmonary 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

Exams 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)
• unusual pattern in iris ("stellate" or star-like)
• partial absence of the teeth, defective tooth enamel, or small, widely-spaced teeth
• heart failure (depending on degree of heart defect)
• high blood calcium level, hypercalcemia, that may cause seizures and muscle rigidity
• hypertension (high blood pressure), depending on degree of blood-vessel narrowing
• echocardiography with Doppler (may show blood vessel narrowing)
• periodic blood pressure check
• kidney ultrasound (some patients have renal defects)
• blood test for chromosome deletion that is called a FISH test (genetic defect found in 99% of patients with Williams syndrome)
• far-sightedness

Treatment

There is no cure for Williams syndrome. Supplemental calcium and vitamin D should be avoided. It is important to treat high levels of blood calcium if present. The blood vessel narrowing can be a significant health problem and is treated based on severity.

Physical therapy is helpful to patients with joint stiffness. Developmental and speech therapy can also help these children; for example, their verbal strengths can help compensate for other weaknesses. Other treatments are individualized based on a particular patient's symptoms.

Coordination of treatment by a geneticist experienced with Williams syndrome can be beneficial.

Support Groups

Williams Syndrome Foundation www.wsf.org 949-UCI-7259

Williams Syndrome Association www.williams-syndrome.org 248-541-3630

Outlook (Prognosis)

Some degree of mental retardation is found in about 75% of patients with Williams syndrome.

Most patients have a shortened life expectancy, due to complications.

The majority of patients do not live independently of care givers.

Possible Complications

• Blood vessel narrowing can cause heart failure.
• Elevated calcium can lead to calcium deposits in the kidney and other kidney problems.
• Abdominal pain is common for a variety of reasons.
• There have been rare cases of children with Williams syndrome having complications, including death, with anesthesia.

When to Contact a Medical Professional

Many of the symptoms and signs of Williams syndrome may not be apparent at birth. Call your health care provider if you child has features that might be suggestive of Williams syndrome. Seek genetic counseling if there is a family history of Williams syndrome.

Prevention

There is no known prevention for the random mutation. If there is a family history of Williams syndrome prenatal genetic testing is available.