Williams syndrome
Incidence
Rarely inherited, recurrence risk < 1%. The incidence depends on the accuracy of diagnosis, but is between 1 in 20,000 to 1 in 50,000 live births.
Clinical Characteristics
Williams syndrome is due to a microdeletion on chromosome 7. It associates several malformations, including cardiopathy (usually supravalvular aortic stenosis), moderate mental retardation, a typical type of abnormal behavior and facial dysmorphysm. Transient hypercalcemia may also be found in infancy, causing vomiting, feeding difficulties, and constipation. The only medical treatment is that of cardiopathy, which may require surgery. Characteristic pattern including neonatal hypercalcemia, characteristic facial appearance, periorbital fullness, prominent lips, stellate irides, early feeding problems and failure to thrive, happy personality in older children, hyperacusis, excellent musical and verbal skills. Neonatal diagnosis of Williams syndrome is difficult unless hypercalcemia is detected. The characteristic face with unusual (star-like) patterns in the iris, strabismus (wandering eye), fullness of tissues around the eye, thickened lips, and long philtrum (crease from the nose to upper lip) may not be obvious until early childhood. The facial appearance of individuals with Williams syndrome changes considerably with age. Life span may be somewhat decreased because of cardiovascular or renal anomalies, but several studies described adults with excellent quality of life. Although supravalvular aortic or pulmonary stenosis, renal artery stenosis, and hypertension may cause problems, childhood is usually dominated more by behavioral than medical concerns. The loquacious, "cocktail-party" manner and happy affect are attractive, but the accompanying hyperactivity, emotional lability, and excessive anxiety may be taxing. Hyperacusis is common, and extreme responses to sounds like those of doorbells or lawn mowers may complicate behavioral management. Small head size with developmental delay is usual, with 59% of children having a global IQ under 70. Many children perform at age-appropriate levels in the areas of visual recognition, expressive language, and verbal recall. The hypercalcemia is still not understood; it seems related to a diminished physiologic response to normal dietary calcium. It may be the cause of acquired coarctation of the aorta that has been described. Later complications include mitral valve prolapse, peptic ulcer, gall stones, obesity, urinary tract infections with bladder diverticular, and diabetes mellitus. Increased excretion of calcium persists in many adult patients, sometimes causing paradoxical release of parathormone. Calcification of the kidney and narrowing of the arteries to the kidney and other organs cause high blood pressure to be a frequent complication, often with onset in the second or third decade. A few patients have had cerebral arterial stenosis with strokes at a young age. Urinary tract anomalies include bladder diverticula (outpouchings) may be found in later life.
Precipitants
none
Provocation Tests
none
Diagnostic Procedures
Special chromosome (FISH) study demonstrating deletion on chromosome 7q including the elastin gene. Over 90% of children with classical Williams syndrome have a detectable 7q deletion; the diagnosis must be clinical in the remaining 10%.