Nature of Prader Willi Syndrome:

By | 20th May 2012


Clinical manifestation:

There are two clinical phases which characterizes PWS as shown in table 1 (Zellweger, 1988):


The two clinical phases of PWS (1)

Phase 1            Moderate to severe neonatal hypotonia

Poor suck

Difficulty in feeding


Marked delayed in motor milestone


Phase 2            Much less hypotonia

Short stature


Increasing obesity

Labile emotions, Stubbornness

Cognitive limitation


1. Adapted from H.Zellweger, (1988)


Development stages:


Prader willi Syndrome has a substantial variations, most individual with disease shows a characteristic course of development and which can be divided in to following periods:




Early childhood

Late childhood





Considering the fetal activity of PWS,most of the cases reported low fetal activity comparing to the other pregnancies. This reflects the very early onset in both aspects of hypotonia and decreased activity levels. Although the index of suspicion is quite low at this time for the presence of PWS, but it can be detected through amniotic and chorionic chromosomal analysis. If the fetus has the chromosomal deletion, there is no treatment (Greenswag & Alexander, 1995), but genetic counseling is advised. It is estimated that 10-40% of PWS births are breech, which indicate motor and cognitive abilities. Presence of polyhydramnios* is often seen. The length of gestation is normal, birth weight may be slightly less than the normal ones and the birth process is also relatively unmark able, with no reports of fetal distress and or delivery complications.



Neonatal usually manifest the following characteristics:

  1. Severe hypotonia
  2. Apgar tend to be low
  3. Problems in thermoregulation
  4. Poor suck (floppiness)
  5. Gastroesophegal reflux
  6. Iron deficiency anemia

A retrospective of these complications in an infant indicates PWS and been treated with subsequent interventions. Proper nutrition and specific feeding methods should be reviewed frequently.


Early childhood:

By 18 months to three years of age feeding difficulties have been replaced by hyperphagia (Greenswag & Alexander, 1990). As the hypotonia diminishes the children with PWS increase motor skills and learn to walk between ages of 2 to 3 years. Dental problems often begin to appear that may be related to poor brushing skills, intrinsic defects, type of food consumed and ability to ruminate (Alexander Greenswag & Nowak, 1987)**. Cognitive and motor delays and possible speech difficulties could be addressed. Most of the children with PWS display stubbornness and aberrant behavior of the age of 3-5 (Greenswag & Alaxander, 1990). Cases of iron deficiency anemia have been seen in diets that are very limited in quantity. Because persons with PWS are less active, hence calcium and vitamin D are essential to prevent the osteoporosis later in life.


Late childhood:

In a study of children with Prader Willi Syndrome in United States and Canada between 7 and 11 years of age, 83% were reported massively obese and 8% were obese (Greenswag & Alaxander, 1990). Without careful management there will be excessive weight gain. Verbal or physical aggressiveness may be seen in almost all cases. Short stature, poor gross motor skills, obesity, mental retardation and underdeveloped genitalia can result in great depression.



Scoliosis may be observed, and usually follows the same course of “idiopathic” scoliosis as in normal teenagers. Individual at this stage of period could be affected with severe to mild hypotonia or osteoporosis. There may be a somewhat longer period of risk because skeletal maturation may not be completed until the early to mid 20s. Teenagers with PWS do not have the surge of sex hormones, due to which males and females do not progress beyond physical and pubic hair development, females do not have menstruation cycle and males testosterone supplementation may reduce the appearance of immature genitalia and increase the growth of body hair, although problems with short stature remains. The obvious physical differences between PWS and normal teenagers can cause emotional distress.***



All affected individuals die young due to complications of morbid obesity like diabetes, cardiac poor respiratory complication. Skin picking behavior problems and food seeking persist. In most of the instances the persistent of above behavior leads to an out-of-home placement. It has been also seen that PWS ages 16 years and beyond who live independently had significantly more obese than those living in more restrictive settings (Greenswag 1984, 1987). The elderly adults with PWS are not well understood. The impact of the lifelong fight with obesity, the hypotonia, difficulty in attaining cardiovascular fitness and natural history of the syndrome itself will become more apparent in the decades to come. It possible that specific medical problem may emerge in elderly PWS population (eg. Osteoporosis, respiratory difficulties, circulatory problems etc.).