DiGeorge Syndrome
This week's "Got Questions?" answer comes from Christa Lese Martin, PhD, (left) associate professor in the department of human genetics, and Opal Ousley, PhD, assistant professor in the department of psychiatry and behavioral sciences, both at Emory University School of Medicine.
Is DiGeorge syndrome an autism spectrum disorder?
DiGeorge syndrome is one of a growing list of genetic disorders whose symptoms sometimes overlap with those of autism. An estimated 15 to 20 percent of those with DiGeorge meet the behavioral criteria for a diagnosis of autism spectrum disorder (ASD). In other words, some but not all individuals with DiGeorge have autism.
DiGeorge is technically referred to as 22q11.2 deletion syndrome (22q11DS). More familiarly it’s been dubbed “22q.” It results from a missing chunk of DNA on chromosome 22. Those with 22q share common features and symptoms. But like autism, the disorder can affect individuals differently. We believe that these differences may be due to modifying effects in each person’s genome, or entire set of genes.
Many children with 22q have some social difficulties, developmental delays or learning disabilities. For the majority, the symptoms are not severe or extensive enough to warrant an autism diagnosis. Individuals with 22q also share common health issues. Many have heart defects and immune problems. Also common are distinct facial and palate features that can affect their ability to speak clearly.
Along with 22q, several other genetic disorders have features of autism. Some affected individuals likewise receive an autism spectrum diagnosis. Examples include fragile X syndrome, Rett syndrome, Prader-Willi syndrome, deletions of chromosome 16p11.2 and duplications of chromosome 15q11-13. Similar to 22q, about 15 to 20 percent of individuals with one of these genetic disorders are on the autism spectrum.
Many of behavioral treatments for autism can help those with 22q or other genetic abnormalities with associated autism symptoms. At the same time, knowing the genetic cause of autism symptoms is vitally important to help parents and health care professionals better predict and treat related issues.
For example, if a baby is born with a heart defect and is then screened for 22q and tests positive, he would have the advantage of receiving very early intervention for autism symptoms should they emerge. If a child with 22q has language delays or articulation difficulty, a speech therapist would know that palate issues may be affecting the ability to speak. Also, individuals with 22q have a higher risk of psychiatric illnesses such as anxiety, depression and schizophrenia. Knowing this, doctors can monitor for symptoms. They may also want to avoid prescribing medications known to trigger or exacerbate psychiatric symptoms.
Indeed, it’s becoming part of standard medical practice to test for underlying genetic causes of autism. Chromosomal microarray testing can detect deletions and duplications. Sequence analysis detects mutations in individual genes.
Ultimately, identifying the genetic causes of autism can lead to the development of drug therapies targeted to specific disorders. Several clinical trials underway for fragile X syndrome have already identified medications with promise for improving associated cognitive and behavioral problems.
For more information on 22q, visit the International 22q11.2 Foundation.
The authors wish to acknowledge Laurie Tarkan and Jessica Sachs for their assistance in preparing this blog post.
Got more questions? Send them to GotQuestions@autismspeaks.org.
