Institutional Price 
4 weeks
CPT Code 
Test Code 
Test Methods 
Deletion/Duplication analysis
Specimen Types Accepted 
Cultured Cells
Extracted DNA

Prader-Willi syndrome (PWS) is a genetic disorder which causes hypotonia and poor feeding in infancy, followed by the development of hyperphagia and subsequent obesity. Physical characteristics of PWS also include short stature, small hands and feet, and a characteristic facial appearance consisting of a thin upper-lip, down-turned mouth, dental crowding, and almond shaped eyes. Developmental milestones are delayed, and learning disabilities are always present, but may vary in severity. Behavioral problems include temper tantrums, obsessive compulsive tendencies, and skin-picking. The majority of cases of PWS are caused by the absence of paternally expressed, maternally silenced genes in the imprinted region located at 15q11-q13. The most common mechanisms for this include a de novo paternal deletion in this region, maternal uniparental disomy (UPD), or an imprinting center defect. Paternal chromosomal translocations can also be observed. Mutations in the paternal copy of the MAGEL2 gene located at 15q11.2 have also been described in patients with classic PWS and patients with PWS-like features. The proportion of PWS associated with MAGEL2 mutations is unknown, but is predicted to be low.