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Children with features of developmental delay (DD) or intellectual disability (ID) should be referred to a paediatrician for a clinical genetics evaluation.1
What do I need to know?
The causes of DD and ID can be genetic, non-genetic (eg fetal alcohol spectrum disorder, congenital infection) or unknown.
Knowledge that DD and ID are caused by an underlying genetic condition may inform:
- the ongoing management of the child’s condition
- parents of future reproductive risk.
There are several genetic causes of DD and ID:
- abnormalities of chromosome number (eg Down syndrome)
- loss (ie deletion) or gain (ie duplication) of part of a chromosome.
- Single-gene disorders
- de novo gene variants (occurring in the child but not inherited from a parent; eg Rett syndrome)
- Inherited causes
Chromosome microarray (CMA) is now considered a first-line genetic test for the investigation of DD, ID, autism spectrum disorder (ASD), and congenital abnormalities.2 CMA does not detect gene variants causing FXS (ie FMR1 gene), so an additional deoxyribonucleic acid (DNA) test must be ordered alongside.
While general practitioners (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 waiting 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:3
- exhibits ID, ataxia, neurodegeneration, or premature ovarian failure consistent with an FMR1 mutation
- has a relative with an FMR1 mutation.
When should I refer?
A genetic cause should be suspected in individuals with DD and any of the following:
- dysmorphic features
- autistic features
- congenital anomalies (eg cleft palate, heart defects)
- a family history of autism, FXS or other developmental/learning disability.
Patients with these features should be referred to a paediatrician or genetics services.
Refer directly to a paediatric neurologist if there is regression of motor skills (eg suspected muscular dystrophy, spinal muscular atrophy).
Resource for patients
Raising Children Network, Developmental delay in babies