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Dual Diagnoses: the Importance of Diagnosis and Treatment

by Bonnie Patterson, MD

In the past, it was thought children with Down syndrome who exhibited autistic behaviors were simply exhibiting these behaviors secondary to severe or profound retardation. We now realize children with Down syndrome can also have true autism spectrum disorder and that this occurrence is not rare. Little has been written regarding the dual diagnosis of Down syndrome and autistic spectrum disorder (DS-ASD), and currently only 12 cases are reported in the medical literature.

Because so little information is available about the incidence and diagnosis of DS-ASD, parents frequently share with me the frustration they feel as they try to understand why their child is not developing in the same way as other children with Down syndrome. Many relate a specific age when their child's development either regressed or slowed. These atypical patterns of development are most often reported in the areas of language and behavior. Parents describe their child as becoming more withdrawn, obsessively attached to certain objects, engaging in repetitive or stereotypic behaviors, not engaging in imaginary play and losing language skills. These are all behaviors classically described in children with autism spectrum disorder.

Professionals are often reluctant to diagnose a child who has Down syndrome with a second serious developmental disorder such as autistic spectrum disorder. Many believe that the behaviors and atypical language development are related to the severe or profound mental retardation they associate with Down syndrome or believe they are "protecting the parents" by not giving a second diagnosis. Our experience has been that the majority of children we see with autism spectrum disorder and Down syndrome are not severely or profoundly mentally retarded, but function in the moderate to severe range of cognitive delay. In addition, parents are relieved when the diagnosis is finally made which helps them understand their child's differences. It also opens the door to investigating and obtaining appropriate intervention services. It is critical for children with Down syndrome and autism spectrum disorder to be identified as early as possible because of the impact on educational and therapeutic interventions, and in some cases the need for further medical assessments and treatments. There are many educational and therapeutic programs that have been developed specifically for children with autism spectrum disorder, including applied behavioral analysis (ABA or Lovass), developmental social programs (Greenspan), sensory integration therapy and picture exchange communication systems (PECS). Without a diagnosis of autistic spectrum, these strategies will probably be overlooked for a child with Down syndrome. It is as important for a child with DS-ASD to access this intervention, and for the family to know what information to research, as it would be for any other child with the diagnosis of autistic spectrum disorder. Additionally, there are some medical tests that may be beneficial in further evaluating and choosing possible medical treatment for a child with autism. Although every child with the dual diagnosis of DS-ASD does not require all of the following, some may need blood lead levels, chromosomes (including DNA probe for Fragile X), urine metabolic screen, MRI scan of the brain or prolonged EEG.

It is important for the medical community to make progress toward a better understanding of this dual diagnosis. With information, we will be able to put some of the disputes regarding occurrence aside and focus on effective medical and educational interventions. For example, there are reports of increased frequency of seizures and abnormal EEG findings in children with autism. The current recommendation is that prolonged EEG studies (23 hours) be done, particularly for those who have a history of language loss or regression. With this in mind, a study is currently underway at the Cincinnati Center for Developmental Disorders evaluating a group of 10 children with DS-ASD with prolonged EEGs. The result of the EEG determines whether or not we should consider treatment with seizure medication. The use of these medications may improve language or behavior if a child with DS-ASD shows evidence of abnormal electrical activity on the EEG. This could be particularly important for children with Down syndrome and autistic spectrum, as the frequency of seizures has been reported to be greater than that of the general population (5-10 percent). The association between autism and epilepsy is also high, with ranges reported from a low of seven percent to a high of 42 percent. Prolonged EEG studies (23 hours) have been found to be better at identifying abnormalities in children with autism over routine EEG studies. The current recommendation for children with autism spectrum is for those with significant expressive and receptive language dysfunction, or a history of regression of language, to receive a prolonged EEG study including a significant amount of sleep recording. It seems only appropriate that children with DS-ASD be evaluated in the same way in order to determine if any abnormalities are detected, which could effect medical management strategies.

Early recognition and diagnosis of autism spectrum disorder in children with Down syndrome has significant implications for a family's understanding of their child's needs in regards to therapeutic and educational interventions, as well as the need for medical evaluations and treatments. Continuing research is needed in the area of dual diagnosis to explore environmental and familial risk factors, MRI findings, biochemical changes and the relationship of the EEG abnormalities to autistic behaviors, particularly in those children with a history of language regression. With this research, we hope to gain a greater understanding of Down syndrome and autistic spectrum disorder, which will help reduce barriers to diagnosis and access to appropriate medical and educational interventions.

Bonnie Patterson, MD, is a developmental pediatrician at the Cincinnati Center of Developmental Disabilities and the director of the Down Syndrome Clinic. She is the co-chair person of the Down Syndrome Medical Interest Group and a member of the Clinical advisory Board for the national Down Syndrome Society.


Bregman J, Volkmar FR. (1988) Autistic social dysfunction and Down syndrome. Journal of American Academy of Child and Adolescent Psychiatry 27:440-41.

Ghaziuddin M, Tsai L, Ghaziuddin N. (1992) Autism in Down's syndrome: presentation and diagnosis. Journal of Intellectual Disability Research 36:449-56.

Howlin P, Wing L, Gould J. (1995) The recognition of autism in children with Down syndrome--implications for intervention and some speculations about pathology. Developmental Medicine and Child Neurology 37:398-414.

Kent L, Perry K, Evans J. (1998) Autism in Down's syndrome: Three case reports. Autism 2(3): 259-67.

Wakabayashi I. (1979) A case of infantile autism associated with Down's syndrome. Journal of Autism and Developmental Disorders 9:31-36.

Tuchman R, Rapin I. (1997) Regression in pervasive developmental disorders: Seizures and epileptiform electroencephalogram correlates. Pediatrics 99:560Xzv vv-66.

Stafstrom C. (1993) Epilepsy in Down syndrome: Clinical aspects and possible mechanisms. American Journal on Mental Retardation. 98:12-26.

The article above is reproduced from the September/October 1999 issue of Disability Solutions, Volume 3, Issues 5-6. Permission was granted for its use on this web site. In accordance with federal copyright restrictions, the contents of this article may not be reproduced by photocopying or any other means without written permission from the copyright holder. © 1999 Disability Solutions

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