Q: My neighbor's daughter seemed fine at birth but never learned to talk. She was just diagnosed with Angelman syndrome. What is this? Will her siblings be affected?

Q: My neighbor's daughter seemed fine at birth but never learned to talk. She was just diagnosed with Angelman syndrome. What is this? Will her siblings be affected?

A: In 1965 Dr. Harry Angelman described several children that had stiff, jerky gaits, lack of speech development and seizure disorders. These children seemed to be prone to spontaneous bouts of laughter as well. In 1987 further research into this condition, now called Angelman syndrome (AS), found it to be due to a defect in chromosome 15.

In general we all have two copies of each gene, one we inherit from our mother and one from our father. The gene on chromosome 15 called UBE3A is quite interesting; the UBE3A gene we inherit from our mother is "expressed" (is the functional one) in several areas of the brain, while the paternal one is inactive. A defect in UBE3A is responsible for AS.

Most cases (about 90 percent) of AS are not inherited, but are due to a deletion in the maternal UBE3A gene (causing it to malfunction) that occurs randomly. That leaves about 10 percent which are inherited. For example, if a man has a defective UBE3A gene he may pass it on to his daughter, who would not have AS since it is the mother's gene that is expressed. If the daughter passes the defective gene on to her child, that child would develop AS. Other modes of inheritance can also occur.

AS is estimated to affect about one in 10,000 newborns; it may be more common than this since some cases may be missed or misdiagnosed as other conditions.

Although infants with AS may have slightly wide mouths and slightly protruding tongues, these features are not easily identified. Since these infants initially have normal development (although some delay in head growth is common and some have feeding problems), AS is not usually identified at birth.

Children with AS have profound limitations in their speech development. Although they are usually not able to use more than a few words in proper context, all AS children can communicate in other ways. AS children also have significant intellectual disabilities. Movement disorders limit their fluidity in walking; although about 90 percent of children with AS can walk, the onset of walking is significantly delayed. Balance and coordination may also be affected.

It is because of these delays in achieving developmental milestones that a diagnosis of AS is suspected, and why it is not typically made until the ages of 2 to 7.

AS children typically have quite happy affects; they laugh and smile frequently (although sometimes inappropriately), often accompanied by flappy hand movements. They may be quite hyperactive when young, although this seems to improve as they age.

Most children with AS develop a seizure disorder (often by age 3), usually with an abnormal EEG. Other conditions, like sleep disorders, strabismus and decreased skin pigmentation are also common.

Since the gene responsible for AS has been identified, genetic testing can be done to verify the specific diagnosis. Genetic counseling can then be offered to the family, and in the cases where the condition is inherited the parents can make an informed decision about future children.

Like many other genetic disorders, there is no specific treatment for AS. However, specialized educational and enrichment programs can help these children maximize their quality of life. Behavior modification therapies may also be useful. Furthermore, having a special needs child in a family brings special joys, but also special challenges. Therefore, family counseling and engagement is a very important aspect of the overall care for AS children.

For those children with a seizure disorder, anti-seizure medication is usually indicated. Physical therapy to prevent orthopedic issues (that may arise because of the movement disorders) can also be very helpful.

AS patients are believed to have a normal life expectancy. The condition does not typically regress as they age, therefore the benefits they achieve from specialized education and enrichment programs are lifelong.

Newborn exams, as well as periodic exams to ensure the child is developing as expected (and to be sure they get all their childhood vaccinations), are important; early identification of any issues allows earlier investigation and intervention.

Jeff Hersh, Ph.D., M.D., F.A.A.P., F.A.C.P., F.A.A.E.P., can be reached at DrHersh@juno.com.