What is PWS?

Physical characteristics:
There is usually a characteristic facial appearance with a narrow forehead, almond-shaped eyes, and a thin upper lip with downturned mouth. However, where children with Prader-Willi syndrome receive growth hormone this is much less obvious. Scoliosis (S-shaped curvature of the spine) may develop. Many individuals with Prader-Willi syndrome who have the deletion type have fairer colouring of their hair, eyes and skin compared to other family members.

Growth deficiency:
People with Prader-Willi syndrome typically have short stature compared to the family height and small hands and feet. Early growth may be below normal, and there is failure to have a pubertal growth spurt, although treatment with daily growth hormone will correct this problem and height may then be normal.

Hyperphagia (drive to eat):
People with Prader-Willi syndrome have an abnormality in the part of their brain (the hypothalamus) that helps determine changes in feelings of hunger before and after eating. They have this continuous urge to eat that is very different from the period of poor eating in the early years. In addition, they need fewer calories to maintain an appropriate weight. This is believed to be due to decreased muscle tone and bulk and lower physical activity.

It is important to provide the needed nutrients while restricting calories in order to maintain a healthy weight. Access to food must be limited and regular (preferably daily) exercise should begin as early as possible. Weight management should be individualised and may include weekly weighing, complete control of food intake and environmental barriers to food access (such as locks on kitchens).

​Incomplete sexual development:
The small genitalia that characterise affected individuals are more easily identified in males, but affect both sexes.  Males often have undescended testicles and a small, poorly delineated scrotum; females have small labia minora and clitoris. Pubertal development is typically delayed and incomplete, and fertility is extremely rare and has occurred only in females.  Hormone treatment during adolescence may be recommended.

Intellectual disability:
Learning, social and cognitive development is delayed and impaired. Although there is wide variability in abilities most people with Prader-Willi syndrome function below what would be expected given their family background and the average IQ for people Prader-Willi syndrome is around 60, which is in the mild intellectual disability range. People with Prader-Willi syndrome may have other specific impairments affecting their social functioning, working memory, and their ability to change their attention from one task to another.

Speech and language difficulties:
The great majority of people with Prader-Willi syndrome develop spoken language and can communicate verbally. Cognitive capacity and probably also the extent of hypotonia may affect the development of these abilities and speech therapy may be helpful and the use of symbols and visual material may be valuable.

Balance and Coordination:
Fine motor skills (the use of hands and wrists to make precise movements) usually are well developed, while gross motor skills (relating to the use of the torso and limbs for example in running and for balance) remain limited.

High pain threshold and irregularities in body temperature control:
Most people with PWS are unaware of injury and infection because of blunted sensory mechanisms and reduced sense of pain. Unexplained high or low temperatures may occur and there is often insensitivity to environmental temperature. Complaints of pain should be taken seriously as when they occur they may indicate serious illness.

Scratching and picking:
Many individuals with Prader-Willi syndrome pick and scratch at sores and insect bites which, if not controlled, may become chronic sores and result in infection.

Behaviour, mental health and temperament:
Children with Prader-Willi syndrome can be loving and happy particularly in the early years. However temper outbursts and subtle changes, typically mood swings and behaviour difficulties may emerge over time.  Some teenagers or adults with Prader-Willi syndrome can develop more serious mental health problems.

Other findings:
People with Prader-Willi syndrome may experience excessive daytime sleepiness and sleep apnoea, particularly if obese. Eye abnormalities such as strabismus (cross-eyed), myopia (near-sightedness) or amblyopia (lazy eye) are common.

Treatment and intervention
There is currently no cure for Prader-Willi syndrome, nor is there a drug that can be prescribed to alleviate all of the symptoms and there is no known treatment to lessen the drive to eat, although much research is being conducted in this area. However, the lives of people with Prader-Willi syndrome can be transformed through having a sound understanding of the syndrome and access to good informed care and support.

​Treatment is primarily symptomatic and most importantly consists of:

• Early diagnosis, provision of information and support with interventions.
• Lifetime weight control through diet, environmental controls (limited access to food), and exercise.
• Growth hormone replacement therapy when available.
• Sex hormone replacement therapy when available
• Support strategies that seek to minimise behaviour difficulties and which support activities and social engagement that helps maintain wellbeing

With appropriate support and information and the effective management of specific aspects of the syndrome, people with Prader-Willi syndrome can expect to live healthy and increasingly long lives.

There is currently no cure for Prader-Willi syndrome, nor is there a drug that can be prescribed to alleviate all of the symptoms. As of this writing, there is no known substance that has been demonstrated to lessen the drive to eat, although much research is being conducted to find such a substance.

Treatment is primarily symptomatic and most importantly consists of:

• Early diagnosis and intervention

• Lifetime weight control through diet, environmental controls (lack of access to food), and exercise

• Growth hormone replacement therapy, when available

• Behaviour management , with consistent limit-setting

• Special education and sheltered or supported employment

Early Diagnosis
Early diagnosis of PWS gives parents an opportunity to manage their child‘s diet, prevent or treat infantile failure to thrive, avoid obesity from the start, and improve behaviour. It may facilitate a family‘s access to critical early intervention services and help identify areas of need or risk. It allows families to know what to expect and institute appropriate preventative measures.

Weight Control
People with PWS have a flaw in the part of their brain that determines hunger and satiety that gives them a continuous urge to eat following their period of poor eating in the early years. In addition, they need fewer calories to maintain an appropriate weight. This is believed to be due to decreased muscle tone and bulk and lower physical activity. It is important to provide the needed nutrients while restricting calories in order to maintain a healthy weight. Access to food must be limited and regular (preferably daily) exercise should begin as early as possible. Weight management should be individualised and include weekly weighing, complete control of food intake, environmental barriers to food access (such as locks on kitchens) and diets acknowledging that fewer calories are required.

Growth Hormone
In recent years, numerous studies have demonstrated conclusively that growth hormone replacement therapy can very positively affect growth, body composition (the proportion of fat to muscle and bone), and activity level in people with PWS. It can also improve breathing and probably also speech and academic performance. Since it can improve body shape and physical abilities, it also improves self-image. However, growth hormone requires a daily subcutaneous injection, is expensive, and is not covered by all health programs in all countries..

Behaviour Management
Behaviour management is crucial for both weight and behaviour problems. Behaviour management should be oriented towards intervention and prevention.  Consistent enforcement of limits by all caregivers (including parents, the wider family, teachers, and residential carers)  is very important. For the best results, make a schedule, plan the day, avoid arguments and anticipate what issues may arise. 

Special Education and Sheltered  or supported Employment
Because of the developmental delay and intellectual disability combined with the behavioural problems, people with PWS require special assistance in school in order to learn as much as their abilities allow. Once they have completed school, they need assistance in finding employment that matches their abilities optimally, and supervision to control access to extra food and deal with behavioural outbursts when they occur. Adults with PWS who do not live with their family will require a residence that includes supportive supervision and accommodation to their dietary and behaviour control issues while simultaneously allowing them as much success and social interaction as possible.

The pattern of characteristics associated with PWS is consistent among those affected by it, although there is significant variability in severity and not all affected individuals have every characteristic.
As a simplification, the disorder is marked by distinctly different presentation in infancy versus later in life.

​Early phase
Initially, the neonate presents with slightly low or normal birth weight and poor suck with subsequent failure to gain weight and grow well, very limp muscles, and delayed developmental milestones. Genitals are often small in both sexes, and one or both testes are undescended in males. Because of the weak, limp muscles and poor suck, infants are almost always unable to nurse and often require special feeding techniques such as special bottles or tube feeding (gavage). The milestones of lifting the head, sitting up, crawling, walking, and speech all tend to be delayed. On average, independent sitting is achieved at around 12-13 months, walking at 24-30 months, and tricycle riding at 4 years. The first word may appear around 21 months and sentences around 3-1/2 years.

Second phase
There follows a period of normal eating behavior and improvement in muscle tone and activity. However, this in turn is followed by a phase that is usually marked by an increased appetite and often a  compulsion to eat. This often occurs in toddlers or young children. Life becomes dominated by a voracious appetite and drive for food. Individuals with Prader-Willi syndrome apparently do not feel full (lack a sense of satiety). They can eat a tremendous amount of food without becoming nauseated or having indigestion – and many have never vomited. This striving for food combined with a lower than normal calorie requirement and, frequently decreased activity related to the hypotonia will result in rapid weight gain if not controlled externally, leading to obesity and eventually the consequences of obesity: respiratory difficulties, heart disease, diabetes, and other problems.