Prader-Willi Syndrome

BACKGROUND

Description and Cause

Prader-Willi Syndrome is a neurobehavioral genetic disorder resulting from one of three genetic causes: (1) a paternal deletion on the long arm of chromosome 15 in 70% of cases; (2) uniparental disomy (both chromosomes 15 of maternal origin) 15 in 25% of cases; or (3) an imprinting defect in 5% of cases. (Note: Angelman Syndrome is often discussed with Prader-Willi Syndrome because they share a similar genetic basis; return to the index to view a document on Angelman Syndrome.)

Diagnosis

Diagnosis is by chromosomal fine structural analysis, fluorescent antibody in situ hybridization (FISH), or DNA probe. DNA probe analysis, where available, is the technique of choice and is required in order to recognize uniparental disomy.

Occurrence

1:10,000 to 1:5,000
Recurrence risk: 0.1%

Characteristic Features

Profound hypotonia in infancy
Feeding difficulties and failure to thrive in infancy
Poor body temperature control
Short stature
Small hands and feet (apparent in childhood)
Thin upper lip and downturned corners of the mouth
Almond-shaped eyes
Narrow bifrontal diameter (forehead)
Hypgonadism (underdeveloped genitalia)
Incomplete sexual development in puberty
Obesity beginning in childhood
Insatiable overeating and desire for food (resistant to diet and behavior modification)
Impulsive, stubborn and perseverative behavior
Skin picking
Decreased sensitivity to pain
Delayed motor development
Speech delay
Mild to moderate mental retardation; range of cognitive functioning from low average with learning difficulties to severe mental retardation

Common Associations

Note: Many of these associations are secondary results of obesity and therefore may be preventable.

Scoliosis
Type II diabetes mellitus in second decade
Pulmonary hypertension
Pulmonary hypoventilation
Pickwickian syndrome
Cor pulmonale
Sleep apnea
Skin sores
Arteriosclerotic heart disease
Osteoporosis
Attention deficit disorder
Premature death

MEDICAL MANAGEMENT CONSIDERATIONS

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Note: These considerations are in addition to the normal medical care provided to an individual without Prader-Willi Syndrome. All recommendations can be addressed through clinical examination by the primary care provider, unless otherwise noted.

General physical health usually remains good in persons with Prader-Willi Syndrome unless obesity becomes severe. Typically, the focus of medical management is on maintaining a strict diet of regular, balanced meals. Food restriction can be very challenging and may impact the entire family system. Siblings, extended family members, neighbors, friends, educators and all other caregivers must receive appropriate education and counseling regarding food restriction and the child’s diet. The need to restrict and/or lock food may complicate family interactions and activities, and may cause stress for everyone involved. Siblings may require special support and counseling to help them understand and adjust to these issues.

Ongoing (all ages)

Recommend a strict diet of regular, balanced meals, making sure caloric intake does not exceed energy requirements (PWS children require fewer calories than normal children)
Recommend consultation by a registered dietician or nutritionist
Monitor weight and height using a PWS growth chart; compare to familial stature
Encourage parents to make sure the child cannot access extra food (teachers and other care providers must be informed also)
Implement applied behavior analysis to manage behavioral problems such as dietary management or skin picking

Infancy (Birth to 1 year)

Perform complete physical and neurological exam to detect congenital anomalies
Consider surgical correction of cryptorchidism
Consider physical/occupational therapy evaluation to address motor delay or feeding difficulties
Ensure adequate nutrition, especially dietary fat intake
Refer to early intervention programs and
Prader-Willi/disability support groups
Provide genetic counseling, including a discussion of recurrence risk
Discuss possibility of SSI enrollment

Early Childhood (1 to 5 years)

Watch for hyperthermia or hypothermia
Screen for scoliosis regularly
Recommend supplemental vitamins
If poor linear growth, test for growth hormone deficiency
Consider speech therapy evaluation
Recommend and arrange for dental care
Implement the recommendations of the physical/occupational therapy evaluation performed in infancy, if applicable
Emphasize the need for strictly enforced rules and limits by all care providers
Consider testosterone injections to increase penile size for independent toileting

Late Childhood (5 to 13 years)

Recommend supplemental vitamins and minerals, especially calcium
If poor linear growth, test for growth hormone deficiency
Recommend 20-30 minutes daily exercise
Screen for scoliosis regularly
Monitor school progress
Monitor speech and language progress

Adolescence and Adulthood (13 years and over)

Recommend 20-30 minutes daily exercise
Recommend supplemental vitamins and minerals, especially calcium
Monitor for increasing behavioral problems
Monitor for decline in cognitive function
Discuss long-term financial plans
Discuss alternative community living resources
Discuss community-supported employment opportunities
Monitor prevocational training and vocational activities

REFERENCES

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Peer-reviewed Journal Articles/Academies

Cassidy, SB. 1997. “Prader-Willi Syndrome.” Journal of Medical Genetics 34 (11): 917-923.

Hanchett, Jeanne MD and Louise Greenswag RN, PhD. 1998. Health Care Guidelines For Individuals With Prader-Willi Syndrome. The Scientific Advisory Board of the Prader-Willi Syndrome Association (USA). Accessed December 2, 1998 at http://www.pwsausa.org/postion/HCGuide/HCG.htm

Hoffman, Carolyn J, et al. 1992. “A Nutrition Survey of and Recommendations for Individuals with Prader-Willi Syndrome Who Live in Group Homes.” Journal of the American Dietetic Association 92 (7): 823-830.

Marin, Andres, et al. 1998. “Prader-Willi Syndrome.” American Journal of Psychiatry 155 (9): 1265-1273.

Tu, Jun-Bi, et al. 1992. “Psychopharmacogenetic Aspects of Prader-Willi Syndrome.” Journal of the American Academy of Child and Adolescent Psychiatry 31 (6) (November): 1137-1140.

Wodarski, Lois Ann, et al. 1988. “Interdisciplinary Case Management: A Model for Intervention for a Patient with Prader-Willi Syndrome.” Journal of the American Dietetic Association 88 (3): 332-335.

Special Interest Groups/Other Publications

Batshaw, Mark L. and Yvonne M. Perret. 1992. Children with Disabilities. Baltimore: Paul H. Brookes Publishing Co., Inc.

Capute, Arnold J. and Pasquale J. Accardo. 1996. Developmental Disabilities in Infancy and Childhood vol. I: Neurodevelopmental Diagnosis and Treatment. Baltimore: Paul H. Brookes Publishing Co., Inc.

Capute, Arnold J. and Pasquale J. Accardo. 1996. Developmental Disabilities in Infancy and Childhood vol II: The Spectrum of Developmental Disabilities. Baltimore: Paul H. Brookes Publishing Co., Inc.

Dambro, Mark R. 1999. Griffith’s 5 Minute Clinical Consult. Baltimore: Lippincott Williams & Wilkins, p. 1218.

Greenswag, LR and RC Alexander. 1995. Management of Prader-Willi Syndrome (2^nd ed). New York: Springer-Verlag.

Hagerman, RJ. 1999. “Angelman syndrome and Prader-Willi syndrome.” In: Neurodevelopmental Disorders: Diagnosis and Treatment. New York: Oxford University Press, pp. 243-290.

Rubin, I. Leslie and Allen C. Crocker. 1989. Developmental Disabilities: Delivery of Medical Care for Children and Adults. Philadelphia: Lea & Febiger.

RESOURCES FOR FAMILIES

California Department of Developmental Services, 916-654-1690, http://www.dds.ca.gov

California Regional Centers, 916-654-1958, http://www.dds.ca.gov/rc/rclist.cfm

Exceptional Parent Magazine, 800-247-8080, http://www.eparent.com/

March of Dimes Birth Defects Foundation, 914-428-7100, http://www.modimes.org

Prader-Willi California Foundation, 800-400-9994, http://www.pwcf.org

The Prader-Willi Connection, 800-358-0682

The Prader-Willi Foundation, Inc., 516-621-2445

Prader-Willi Syndrome Association (USA), 800-926-4797, http://www.pwsausa.org

ADVISORY COMMITTEE

Theodore A. Kastner, M.D., M.S.
Felice Weber Parisi, M.D., M.P.H.
Robin L. Hansen, M.D.
Joan M. Reese, M.D., M.P.H.

PUBLICATION INFORMATION

Funded by a grant from the California Department of Developmental Services

For more information, contact:

Center for Health Improvement
1330 21st Street, Suite 100
Sacramento, CA 95814
(916) 901-9645

This document does not provide advice regarding medical diagnosis or treatment for any individual case, and any opinions or statements contained in this document are not intended to serve as a standard of medical care. Physicians are encouraged to view the considerations presented in this document in light of evolving scientific information. This document is not intended for use by the layperson. Reproduction of this document may be done with proper credit given to California Department of Developmental Services and the Center for Health Improvement.