Genomics in general practice

Autism spectrum disorder

Genomics in general practice
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  1. Summary of genetic testing
  3. Figures and tables
  4. Provided under licence

Last revised: 30 Nov 2018

Practice point

Referral to a paediatrician for a clinical genetics evaluation of children with autism spectrum disorder (ASD) can provide a specific diagnosis in between 30 and 40% of cases.1

General practitioners (GPs) can order a chromosome microarray (CMA) at the point of referral to a paediatrician in order to speed up this process.
 

ASD is an umbrella term for a collection of pervasive developmental disorders. This term replaces previously used diagnostic terminology, including autistic disorder, Asperger syndrome, Rett syndrome, childhood disintegrative disorder and pervasive developmental disorder – not otherwise specified.2

ASD is characterised by impaired social communication and interaction, limited interests, and repetitive behaviours. Markers of ASD usually appear during the first two years of life, in particular, problems with language development and social relatedness.3

Some rare genetic conditions show clinical features that are characteristic of ASD. These include:

  • tuberous sclerosis (TSC1 or TSC2 genes)
  • Fragile X syndrome (FXS; FMR1 gene)
  • chromosomal abnormalities (eg inversions, duplications)
  • metabolic conditions
  • Rett syndrome (MECP2 gene in many cases).

CMA is now considered a first-line genetic test for the investigation of developmental delay (DD) and intellectual disability (ID), ASD, and congenital abnormalities (CMA).4 A CMA does not detect gene variants causing FXS (a single-gene cause of ASD), so an additional deoxyribonucleic acid (DNA) test must be ordered alongside.

While GPs are able to order CMAs, many choose not to, given the complex interpretation of the results. However, ordering CMA and FXS tests in parallel with referral to a paediatrician can reduce wait times for patients. A Medicare Benefits Schedule (MBS) rebate is available for CMA in situations where the patient has DD, ID, ASD or at least two congenital abnormalities. DNA testing for FXS is available with an MBS rebate when the patient:5

  • exhibits ID, ataxia, neurodegeneration or premature ovarian failure consistent with an FMR1 mutation
  • has a relative with an FMR1 mutation.

Refer to:

  • a paediatrician for assessment of autistic features
  • genetics services if the individual is dysmorphic
  • a neurologist if regression of psychomotor skills occurs.

If a diagnosis of ASD is made, referral to a genetic counsellor may be appropriate in terms of family planning. Research estimates the recurrence risk for siblings of children affected with ASD at up to 7%. If there are multiple affected siblings, the recurrence risk is higher (up to 50%).1

Information

Autism Spectrum Australia (Aspect), What is autism?
Centre for Genetics Education, Autism spectrum disorder

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Autism Spectrum Australia (Aspect)

  1. Schaefer GB, Mendelsohn NJ. Clinical genetics evaluation in identifying the etiology of autism spectrum disorders: 2013 guideline revisions. Genet Med 2013;15(5):399–407.
  2. American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 5th edn. Washington, DC:American Psychiatric Publishing, 2013.
  3. Tonge B, Brereton A. Autism spectrum disorders. Aust Fam Physician 2011;40(9):672–77 [Accessed 15 December 2017].
  4. Miller DT, Adam MP, Aradhya S, et al. Consensus statement: Chromosomal microarray is a first-tier clinical diagnostic test for individuals with developmental disabilities or congenital anomalies. Am J Hum Genet 2010;86(5):749–64. [Accessed 15 December 2017].
  5. Department of Health. Medicare Benefits Schedule (MBS) Online. Canberra: DoH, 2017 [Accessed 15 December 2017].
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