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Diagnosis
Diagnosis/testing
PWS should be considered when presented with a hypotonic (floppy) newborn.
Accurate consensus clinical diagnostic criteria exist, but the mainstay of
diagnosis is genetic testing, specifically DNA-based methylation testing to
detect the absence of the paternally contributed Prader-Willi syndrome/Angelman
syndrome (PWS/AS) region on chromosome 15q11-q13. Such testing detects over 97%
of patients. Methylation-specific testing is important to confirm the diagnosis
of PWS in all individuals, but especially those who are too young to manifest
sufficient features to make the diagnosis on clinical grounds or in those
individuals who have atypical findings.
PWS phenotype
The classic PWS presentation includes:
* short stature
* small hands and feet
* hypotonia and poor muscle development
* excess fat, especially in the central portion of the body
* narrow forehead
* almond shaped eyes with thin, down-turned lips
* light skin and hair relative to other family members
* lack of complete sexual development in adolescence
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