Prader- Willi Syndrome
Summary and Description
What is it?
A complex, mulit-system genetic disorder affecting appetite, growth, metabolism, cognitive function and behavior.
Patients exhibit the following KEY characteristics:
- Infantile hypotonia (low tone)
- Developmental delays and intellectual disability
- Behavioral disorders
- Characteristic facial appearance
- Obesity (due to insatiable hunger and slowed metabolism)
- Hypogonadism
- Short stature
**People with Prader-Willi Syndrome do not recognize the feeling of being full after eating
(Lewis, Freebarirn, Heeger, & Cassidy, 2002)
image sources: http://geneticsperiod4.wikispaces.com/Prader-Willi+Syndrome (above)
4 Distinct Nutritional Phases
Not all adults reach stage 4- in fact, most do not
image source: http://www.nature.com/gim/journal/v14/n1/fig_tab/gim0b013e31822bead0t1.html (below)
How does it happen?
It is the result of the loss of function due to imprinted genes on chromosome 15- it is the first known human genomic imprinting disorder.
Can occur one of three possible ways:
- The paternally contributed associated region of chromosome 15 is deleted (70% of cases)
- Two copies of chromosome 15 are inherited from the mother, and no copy inherited from the father aka. Maternal UPD (25% of cases)
- Imprinting deficits: a structural abnormality of chromosome 15 or an error in the process of activating paternal genes (5% of cases)
(Lewis et al, 2002)
It is estimated that 1 in every 12,000- 15,000 people are living with Prader- Willi Syndrome
- It effects men and women equally
- It is seen worldwide among all races
- It is the most common identified genetic cause of obesity