If you think your child may have PWS, check the diagnostic criteria to prompt further testing

This can be confirmed by genetic testing

Methylation analysis will detect more than 99% of cases, including all of the major genetic subtypes of PWS (deletion, uniparental disomy, or imprinting mutation). A FISH (fluorescent in-situ hybridization) test will identify those patients with PWS due to a deletion, but it will not identify those who have Prader-Willi syndrome by UPD (uniparental disomy) or an imprinting error.