Autism Spectrum Disorder

Overview

Autism Spectrum Disorder (ASD) occurs more often in children with Down syndrome than in other children. The prevalence of autism among people with Down syndrome has been estimated from studies in the UK and Brazil to be about 6–7% (Kent et al.1999; Lowenthal et al. 2007), a 10-fold increase from the general population.

The dual diagnosis of ASD and Down Syndrome can be extremely disabling. Added to this, these children have an increased risk of more severe learning difficulties as compared to those children with Down syndrome who do not have autism. Studies have shown that deficits in reciprocal social interaction and communication and the increase in repetitive and restricted behaviours, the core features of autism, are not simply a function of their more severe intellectual impairment.

Children with Down syndrome, who have the dual diagnosis of an Autism Spectrum Disorder, tend to receive the diagnosis of ASD at an older age than their peers. Their parents and carers may experience a long wait and considerable difficulty in obtaining the diagnosis.

Recognising ASD in children with Down syndrome is challenging. There can be a reluctance to consider the possibility of co-existent Down syndrome and ASD. There are several reasons why the diagnosis is frequently much delayed, including:
• the belief that children with Down syndrome are always ‘sociable’ and friendly, so cannot be ‘autistic,’
• the complexity of diagnosis of neurodevelopmental disorders in association with significant developmental delay
• communication difficulties thought to be due primarily to be due to delay of speech and language
• lack of awareness of the usual developmental profile of children with Down syndrome.

This diagnostic overshadowing can delay the diagnosis of ASD and the understanding and intervention strategies that these children need.

There are a number of recognised risk factors for autism, in children with Down Syndrome. These include:
• Seizures, particularly West syndrome (infantile spasms)
• Early Hypothyroidism
• Post cardiac surgery complications
• Severe learning difficulties/ lower IQ
• First or second-degree relatives with the autism phenotype

Children may display behaviours typical of autism 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 noted in later childhood.

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

• There are several important conditions to consider in evaluating a possible dual diagnosis of autism and Down Syndrome. These are more common in Down Syndrome and may cause diagnostic confusion or increased disability. These include:
• Hearing impairment
• Visual impairment
• Hypothyroidism
• Major concurrent illness
• Profound and severe multiple physical disability
• Severe learning difficulties
• Social deprivation/neglect
• Attachment disorders
• ADHD
• Mood disorders

Diagnosis is important because when the two conditions coexist Autism Spectrum Disorder takes precedence in terms of educational, behavioural and therapy needs.

Assessment
Information from multiple sources is be useful for making the diagnosis of ASD.
Studies have shown that clinical judgment of a multidisciplinary team following DSM-V or ICD-11 criteria supported by the standardised assessments are helpful.
For moderate to severe degrees of intellectual impairment, ADOS and ADI-R combined in assessments have been demonstrated to perform well in children and adolescents (ages 5–20 years) with intellectual disability.

Presentations at DSMIG Meetings

Materials from this meeting are available for members only who need to log in to access them. For details on how to become a member click here.

 

Additional Resources

Autistic Disorder and Down’s syndrome Dr Jennifer Dennis .Down’s syndrome association Journal no.128 (2013)

 

Autism and Down syndrome Professor Sue Buckley. Down syndrome news and updates (2005 )

 

Autism spectrum condition, complex needs and visual resources

Understanding dual diagnosis of Down’s syndrome and autism spectrum condition training days for parents and professionals through DSA.Gillian Bird, Down Syndrome Association Training Services Manager

 

Autistic-Spectrum Disorders in Down Syndrome:Further Delineation and Distinction from Other Behavioral Abnormalities

 

Down’s syndrome and autistic spectrum disorder: a look at what we know.  Capone G. (2001) NDSS website

 

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

 

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

 

Book Chapter

Developmental, Psychological and Psychiatric Function. Jeremy Turk

in
Down Syndrome – Current Perspectives MacKeith 2015
Edited by Richard Newton , Shiela Puri and Liz Marder