Prader-Willi Syndrome

DEFINITION. Prader Willi Syndrome (PWS) is a genetic disorder due to a deletion or absence of a portion of chromosome 15.


CLINICAL PRESENTATION. The classic neonatal presentation of PWS is profound hypotonia, abnormal, weak, or absent cry, diminished deep tendon reflexes, poor feeding, below-average weight, and often a history of fetal inactivity. The infants are so “floppy” that they have little facial expression and gross motor development is delayed. Between 1 and 3 years of age, the uncontrollable hunger drive replaces the feeding difficulties of the neonatal period. Initially parents and health care providers are delighted to see children with PWS eat after struggling with feeding techniques and NG tubes during the first year of life. Around two years of age, excessive weight gain is observed, and later on obesity becomes obvious as toddlers with PWS become obsessed with food. As their motor skills increase, so do their food-seeking strategies. In the school setting, children with PWS find ways to get food. Increased body fat is observed, characteristically distributed in the trunk and thighs while the lower arms and legs remain lean. While affectionate and cooperative, most children with PWS present with mild to moderate mental retardation (mean 65-70) in addition to short-term memory deficits and learning disabilities. Special education programs taking into account the child’s cognitive limitations are often initiated in late childhood. By adolescence, constant efforts to satisfy hunger result in aggressive and bizarre food-seeking activities. Accompanying the uncontrollable hunger is decreased calorie utilization, largely due to inactivity. During this stage many adolescents with PWS develop personality problems ranging from being dull, lethargic, and indifferent to being clever, secretive and manipulative. Transitioning from one activity to another is difficult, and signs of depression and occasionally rage episodes may emerge. Reduced bone mineral density is typically present, and this may lead to osteoporosis and osteopenia. Problems with sleep including daytime sleepiness and sleep apnea are common, and most adolescents also present with skin picking, thick viscous saliva, hypopigmentation, and scoliosis and/or kyphosis. 


INTERVENTION. The treatment of PWS is a challenge given the extent of the functional and metabolic limitations associated with the condition. There is no cure for PWS nor is there one medication to treat all symptoms, but several strategies are available to manage specific symptoms. Since the severity of the associated health problems is directly related to the degree of obesity, nutritional intervention is the key component of any treatment program. Caloric intake should be maintained between 600 to 800 kcal for younger children and between 800 to 1300 kcal for older children and adults. Aggressive management and control over availability of food needs to be incorporated into residential, school, and work environments. Appetite-suppressants and gastric surgery are both ineffective in controlling overeating in individuals with PWS, but a behavior modification plan that rewards positive behaviors may be beneficial for some patients. Structured physical activity programs to increase energy expenditure and build muscle mass can also be initiated and may sustain the individual with PWS if it is well defined and easy to accomplish. Other endocrine treatment interventions that should be considered include the use of growth hormone for short stature, androgens and/or estrogens to help prevent osteoporosis, early identification and treatment of diabetes with weight loss and medication, and ongoing monitoring and management of osteoporosis.