Autism spectrum disorder

Autism spectrum disorder

PRACTICE POINT

Referral to a paediatrician for evaluation of children with autism spectrum disorder (ASD) can provide a specific diagnosis in between 30 and 40% of affected individuals. General practitioners (GPs) can order a chromosome microarray (CMA) and testing for fragile X syndrome at the point of referral to a paediatrician in order to speed up this process.

What do I need to know?

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

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

Some rare genetic conditions can show clinical features of ASD. These include:

  • tuberous sclerosis (TSC1 or TSC2 genes)
  • fragile X syndrome (FXS; FMR1 gene)
  • chromosomal abnormalities
  • metabolic conditions
  • Rett syndrome (MECP2 gene variants in most cases).

Genetic testing

CMA is now considered a first-line genetic test for the investigation of developmental delay (DD) and intellectual disability (ID), ASD, and congenital abnormalities. A CMA does not detect FXS (a single-gene cause of ASD), so genetic testing for FXS should be ordered as well as a CMA.

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:

  • exhibits ID, ataxia, neurodegeneration or primary ovarian insufficiency consistent with an FMR1 mutation
  • has a relative with an FMR1 mutations

When should I refer?

Refer to:

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

Other considerations

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 25%, with higher risk for male than female siblings. If there are multiple affected siblings, the recurrence risk is higher (up to 50%).

Further reading

  • Schaefer GB, Mendelsohn Clinical genetics evaluation in identifying the etiology of autism spectrum disorders: 2013 guideline revisions. Genet Med 2013;15(5):399–407.
  • Vorstman JAS, Parr JR, Moreno-De-Luca D, et al. Autism genetics: opportunities and challenges for clinical translation Nat Rev Genet. 2017 Jun;18(6):362-376.
  • Thapar A, Rutter M. Genetic Advances in Autism. J Autism Dev Disord. 2021 Dec; 51(12):4321-4332
  • Genovese A, Butler MG. Clinical Assessment, Genetics, and Treatment Approaches in Autism Spectrum Disorder (ASD). Int J Mol Sci. 2020 Jul; 21(13): 4726.