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  • Prader-Willi Syndrome (PWS)


  • 759.81 Prader–Willi syndrome1


  • Q87.1 Congenital malformation syndromes predominantly associated with short stature2


  • 5C: Impaired Motor Function and Sensory Integrity Associated with Nonprogressive Disorders of the Central Nervous System—Congenital Origin or Acquired in Infancy or Childhood


A 3-month-old infant is referred to physical therapy for examination due to hypotonia. The infant is diagnosed with failure to thrive and difficulty feeding resulting in placement of a gastrostomy tube (G-tube) to assist with weight gain and growth. The mother reports no difficulty with pregnancy and delivery. Upon examination, the infant has poor head control and is unable to achieve prone-on-elbows. After several months, the infant is referred to a geneticist and ultimately, the infant is diagnosed with Prader–Willi syndrome. The infant receives physical therapy through an early intervention program and continues to exhibit developmental delay.

FIGURE 251-1

Examples of structural chromosomal abnormalities: (A) Deletion, (B) duplication, (C) inversion, (D) ring chromosome, (E) translocation, and (F) insertion. (From Hay WW Jr, Levin MJ, Deterding RR, Abzug MJ, Sondheimer JM. Current Diagnosis & Treatment: Pediatrics. 21st ed. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.)



  • Lack of impression from several imprinted genes3

  • Genetic disorder characterized by

    • Specific facial features such as almond-shaped eyes

    • Hypotonia

    • Hypogonadism

    • Strabismus4

    • Short stature

    • Cognitive deficits

    • Inability to regulate appetite

    • Males with undescended testicles5

    • Small hands and feet4,5

Essentials of Diagnosis

  • Two stages3,6

    • Stage 1 occurs during infancy with hypotonia and poor suck/swallow reflex that may result in failure to thrive

    • Stage 2 generally begins at about 2 years of age with lack of satiety progressing to obesity

General Considerations

  • Growth hormone deficiency4

  • Often develop complications from obesity and osteoporosis with age7


  • 1 in 15,0006

  • Affects females and males equally



  • Poor suck/swallow at birth

  • Hypotonia in infancy

  • Specific facial features such as almond-shaped eyes

  • Hypogonadism

  • Strabismus4

  • Short stature

  • Obesity

  • Cognitive deficits

  • Inability to regulate appetite

  • Hypogenitalism/Males with undescended testicles5

  • Small hands and feet4,5

  • Developmental delay

Possible Contributing Causes

  • Deletion in portion of chromosome 15q114

  • Possibly due to dysfunction of hypothalamus6

Functional Implications

  • May ...

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