Prader-Willi syndrome
Overview
Prader-Willi syndrome (PWS) is characterised by severe hypotonia and feeding difficulties in early infancy, followed in later infancy or early childhood by excessive eating and gradual development of morbid obesity. All individuals have some degree of cognitive impairment. PWS has multiple genetic causes, all affecting chromosome region 15q11.1-q11.3. Whilst the SNRPN gene is the site used for testing, PWS is a multigenic disorder.
Test type
Genome-wide chromosome microarray (molecular karyotype)
MLPA & Methylation MLPA
Genes tested
Turnaround time
Up to 6 weeks.
Cost
Bulk billed where eligible
Microarray: non Medicare up to $394.55
Methylation MLPA: non Medicare $230.96
Relevant links
Notes
The recommended first tier test for PWS is a chromosome microarray. The majority of PWS cases (80%) are caused by deletions which can be identified by microarray. This test can be bulk-billed for eligible patients.
If a deletion is not found by microarray testing, methylation analysis can then be requested to exclude maternal uni-parental disomy (UPD) or imprinting centre mutations (accounting for <1% of cases). A second referral is required so the methylation analysis can be bulk-billed for eligible patients.