Down's Syndrome: Autistic Spectrum Disorder

Autistic spectrum disorder - hereafter called autistic disorder - occurs more often in children with Down's syndrome than in other children but less often than in other learning disabled groups.

Prevalence may be as high as 5%

There is often reluctance to consider the possibility of dual diagnosis of Down's syndrome and autistic disorder. For this reason diagnosis is frequently much delayed.

Two reasons for failure to diagnose autistic disorder in children with Down's syndrome are:

1. the misplaced notion that children with Down's syndrome are always 'sociable' therefore they cannot be 'autistic'
2. lack of awareness of the usual developmental profile of those with Down's syndrome.

As with other children neurobiological factors rather than severe intellectual disability most frequently underly the condition. Of particular importance is the relatively high prevalence of infantile spasms.

Children may display behaviours typical of autistic disorder in infancy or as toddlers and follow a course similar to that seen in other children. However it is not unusual for the condition to be heralded by regression of social and communication skills in later childhood - typically between age 3 and 7 years, but sometimes as late as the teenage years. The condition can be extremely disabling.

Diagnosis is critically important because when the two conditions coexist autistic disorder takes precedence in terms of educational and management needs.

The possibility of autistic disorder must be considered in any preschool child with Down's syndrome who is failing to make expected progress in speech, language and communication and social skills and in any older child who shows regression of these skills.

Differential diagnosis includes:

• Hypothyroidism
• Profound and severe multiple disability
• Social deprivation/neglect
• Major concurrent illness
• Hearing or visual impairment

The above information is supported by the following papers:

Capone G. (2001) Down's syndrome and autistic spectrum disorder: a look at what we know. Down's Syndrome Association Journal. Issue 97. Summer 2001. 6-13 (PDF. Reproduced on this site by permission)

Howlin P, Wing L, Gould J (1995) The recognition of autism in children with Down syndrome: implications for intervention and some speculations about pathology. Dev Med and Ch Neurol. 37 406-414

Rasmussen P, Borjesson O, Wentz E, Gillberg C. (2001) Autistic disorders in Down's syndrome: background factors and clinical correlates. Dev,Med, Ch,Neurol. 43 750-754

(J Dennis 24.01.02)

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