Genetic Causes of Intellectual Disabilities: Williams Syndrome
Williams syndrome is a relative newcomer to the field of intellectual disability (ID, formerly mental retardation). It was not identified until 1961. The cause of the disorder is a mutation of chromosome 7. A fragment of chromosome 7 is missing. The mutation seems to be random rather than inherited.
Williams syndrome is not nearly as common as Down syndrome. An estimated 1 in 20,000 babies are born with the disorder. The condition it not limited to any specific group. It occurs equally in males and females. It is not associated with any particular race.
The facial features are subtle but distinct. They include a tiny upturned nose. The mouth is wide and full, with a small chin. The skin around the eye is distended. If eyes are light-colored, a white starburst design may be visible. The neck is longer than normal. The shoulders are sloping. The spine tends to curve and stature is short. There is limited mobility in the joints.
The physical and facial features are very subtle at birth. It usually takes a trained eye to spot them. A geneticist or a birth defect specialist is typically the first to recognize the traits. The physical and facial traits are more easily recognized as the child gets older. This is because of the irregular body proportions become more apparent.
Several medical problems develop along with this disorder. Cardiovascular disease results from narrowed arteries. Stomach problems are common. Infants can be very colicky. Young adults continue to experience abdominal pain. Diabetes is another common complication. Children with this condition usually develop diabetes by age of 13. Hearing loss is also common. These medical problems usually cause a premature death.
The pattern of delayed development is similar to other causes of ID. Delays in motor skills include including walking and toilet training. Some early deficits improve with age. Although speech develops more slowly, expressive language later becomes a strength. However, thinking remains concrete. Therefore, figurative speech, such as metaphor, is difficult to grasp. The attention deficit hyperactivity disorder (ADHD) is more common. However, attention tends to improve with age. Children can have both diagnoses (ADHD and ID).
Typical personality traits are easily recognized. Children tend to be very friendly and lovable. Their endearing qualities are enhanced by good communication skills. Unfortunately, these same traits also make them vulnerable to victimization. Children with Williams syndrome often show no fear of strangers. They can be too friendly and empathetic for their own good. Children with Williams syndrome typically prefer the company of adults to peers. This can cause social problems with their peer group. Sometimes they become highly anxious during stressful or unfamiliar situations.
Adults have varying abilities for independent living. Some live independently or in group homes. Others remain with family or require a primary caregiver. Many are able to complete their academic education and to sustain employment.