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Autism in Children with Down Syndrome

Interactive Autism Network at Kennedy Krieger Institute
Date Published: 
September 26, 2013

Children with autism spectrum disorder (ASD) sometimes have other medical conditions. One of those possibilities is Down syndrome, which is marked by intellectual disability. The occurrence of these two conditions can present special challenges for families. In an interview with the Interactive Autism Network (IAN), George T. Capone, M.D., director of the Down Syndrome Clinic at the Kennedy Krieger Institute in Baltimore, Maryland, explains how the combination of these conditions can affect children, and how they can be treated.

Photo of Dr. George CaponeIAN: How common is ASD in children with Down syndrome?

Dr. Capone: I can't say with certainty, but somewhere between five and 10 percent of children with Down syndrome may meet the criteria for an autistic condition.

IAN: Why are some children with Down syndrome susceptible to autism?

Dr. Capone: No one really knows the answer to that. People have approached it from a number of different vantage points. Some think it is related to some of the co-occurring medical conditions. That would probably be true in the case of infantile spasms, a type of epilepsy seen in very young children, which are associated with autism spectrum behaviors as a long-term outcome. It would appear that whatever the mechanism, it is related to the way the genes on Chromosome 21 interact with other genes on the other 22 pairs of chromosomes, resulting in a differently-organized brain compared to typically-developing children with Down syndrome. (People with Down syndrome have an extra copy of Chromosome 21).

IAN: How does autism manifest itself in children with Down syndrome?

Dr. Capone: In the majority of children in this sub-group, you have developmental delay with marked social-communication impairment and behaviors that look like autism. In this scenario the child develops atypically, with a lack of joint attention or social-communication skills that becomes notable by 15 to 18 months of age, sometimes sooner. Other times, children experience a regression after they've developed somewhat typically for someone with Down syndrome. The regression may come later, typically between ages three and six years, as opposed to 18 months or 24 months as seen in the general ASD population. Another scenario would be the child with infantile spasms who, even once the seizures are managed and controlled, continues to develop in an unusual way.

IAN: What is the gender ratio in terms of the prevalence of Down syndrome and autism?

Dr. Capone: It seems to be about three or four to one, with males predominating.

IAN: Why are children with Down syndrome and ASD diagnosed later than children with just Down syndrome or just ASD?

Dr. Capone: There are a couple of reasons. One, if it's related to a regression-type of phenomenon, it may not occur until a later age, say three to six years. Two, people sometimes expect a certain degree of dysfunctional or atypical behavior in children with Down syndrome, especially if they appear to be developmentally lower-functioning in terms of their adaptive and speech and language skills. So, in other words, there's been a higher tolerance for atypical development in people who already have a diagnosis of Down syndrome. It's probably worth noting that not all lower-functioning children with Down syndrome have a high degree of autism-like behaviors, and not all children with autism-like behaviors are necessarily lower-functioning.

The first step would be in questioning the logic of that presumption and rephrasing it as, ‘If this child with Down syndrome is so unusual compared with 80 or 85 percent of the rest of the children with Down syndrome, maybe we owe it to ourselves and to them to try and understand that better.' So for me the first step is to label or classify that child differently as Down syndrome plus ASD, or dual diagnosis.

IAN: What are the challenges to diagnosing someone with Down syndrome and ASD?

Dr. Capone: It's not clear if the standard instruments for diagnosing ASD, the Autism Diagnostic Observation Schedule and the Autism Diagnostic Interview, are intended for people with severe or even profound levels of intellectual disability. It is difficult to tease apart the atypical social communication and poor reciprocity part of autism from other aspects of intellectual disability that we see in Down syndrome. This makes diagnosing ASD in a child with Down syndrome problematic. Another reason could be that the possibility that a child with Down syndrome could also have ASD is not thought of frequently enough yet.

IAN: What can be the consequence of not diagnosing autism in someone with Down syndrome?

Dr. Capone: The biggest implication is for the early intervention program and the Individualized Education Program (IEP) because these children need something above and beyond standard interventions for developmental delay, such as addressing maladaptive behaviors, deficits in functional communication and daily living skills. Another aspect of having an autism diagnosis is that it should put you on high alert for other conditions such as sleep problems, anxiety and mood disorders and, of course, maladaptive behaviors generally.

IAN: How can parents tell if their child with Down syndrome has autism?

Dr. Capone: It depends a little bit on how familiar they are with children with Down syndrome. The parents who are part of a parent network or support group will be around other children with Down syndrome, and they will come to know if their child is similar or not to those other kids. This is often when suspicions that a child may have autism first begin. An extreme situation would be a family living in a more isolated area that doesn't have a community of parents or children whom they interact with. When that happens, you don't have the benefit of early recognition and implementation of some autism-specific interventions, such as teaching functional communication skills or trying medication.

IAN: What kind of medication is available?

Dr. Capone: There are medicines for insomnia and sleep maintenance. For children with a high degree of impulse dyscontrol and disruptive behavior, you may need to use medications for Attention Deficit Hyperactivity Disorder. If there is a high degree of cognitive and attentional disorganization with stereotypies [repetitive movements or speech] and sensory-related behaviors, we may try atypical antipsychotic medications. I am very cautious about the use of stimulant or antidepressant medications in these children. Sometimes we use mood stabilizers for children who are very irritable and have self-injurious behavior, especially if they've had a history of infantile spasms. Whatever the medications, they are adjusted frequently according to the child's individual needs and any negative side effects. The question is: can you even find a medication that is helpful with certain target behaviors and has an acceptably low side-effect profile? Unfortunately, not always.

IAN: What do you do in those cases where medication is not helpful or if a parent chooses not to use medication?

Dr. Capone: You may continue to rely on other types of intervention, like behavioral support, sensory–based treatments, functional communication and additional training for teachers in the classroom. It's not as if you do one intervention at the exclusion of the other. It's quite common that you're using some combination of all of the above.

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