Prader-Willi syndrome (PWS)

PWS is characterized by central hypotonia and feeding difficulties during infancy followed by excessive eating, rapid weight gain, and central obesity in early childhood. Children with PWS exhibit characteristic facial features including bitemporal narrowing, almond-shaped palpebral fissures, and a down-turned mouth. Additional diagnostic characteristics of PWS include global developmental delay, mild to moderate intellectual disability, distinctive behaviors, short stature, hypopigmentation relative to other family members, small hands and feet, and hypogonadism manifesting as genital hypoplasia, incomplete/delayed puberty and, in the majority of cases, infertility. The neurobehavioral phenotype in individuals with PWS includes hyperphagia, temper tantrums, aggression, specific repetitive and ritualistic behavior, stealing and lying, skin picking, mood and sleep disturbances. Consensus diagnostic criteria were first established in 1993 and revised in 2001 to aid in the recognition of the disorder.

Tests Available

Forms and Documents

Test Details

  • Confirmation of clinical diagnosis
  • Targeted testing for a known familial deletion, UPD or imprinting error
  • Prenatal diagnosis by targeted array CGH for deletions or UPD only (methylation analysis not available for prenatal).


3-4 weeks
2-5 mL Blood - Lavender Top Tube
Buccal Swabs


  • 315.3 Developmental speech or language disorder
  • 759.8 Other specified anomalies
  • 315.9 Unspecified delay in development, Developmental disorder NOS, Learning disorder NOS
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