Prader-Willi Syndrome

A practical guide

Jackie Waters

• Publisher: David Fulton Publishers
• Year: 2014
• ISBN:
  9781134110131
• Edition: 1
• Topic: Education
• Subtopic: Education General

An examination of the cognitive, medical and psychological aspects of educating a child with Prader-Willi Syndrome. Practical advice is given for every part of the schooling process, from classroom management to helping the child with difficult lessons such as maths. The section on further education discusses the ethical issues concerned with learning skills for independent living and the potential for future employment.

Chapter 1

An Introduction to Prader-Willi Syndrome

This introduction provides an overview of the genetic, physical and psychological basis of Prader-Willi Syndrome (PWS). A general knowledge of these characteristics is essential, as the child with PWS needs to be understood within the context of the challenges placed on them by the syndrome. However, although many of the child’s behavioural problems and cognitive abilities are explicable within this framework, other influences such as social and family environment, as well as hereditary factors, have their part to play in producing an overall picture of the child. These also need to be taken into account. Hence, while each child with PWS has some of the characteristics of the syndrome, they still remain very much individuals.

History, incidence and prevalence

Prader-Willi Syndrome (PWS) was first described by Swiss doctors, A. Prader, A. Labhart and H. Willi in 1956 (Prader et al. 1956). During the early 1960s, Dr Bernard Laurance reported several children in England with the features of what we now know to be Prader-Willi Syndrome, but it was not until later in that decade that doctors in the rest of the world became aware of it (Laurance 1961).

Even then, knowledge about the syndrome was scarce, tending to concentrate on those who were most severely affected, with the result that it was considered to be a syndrome which produced moderate to severe learning difficulties. Research has been more widely undertaken only within the last ten to fifteen years. The greatest advances have been made in the field of genetics, and it is much more recently that attention has begun to focus on the psychological and cognitive aspects of the syndrome. Since then, many cases have been reported of people whose intellectual abilities are within the borderline to low average range.

It is now acknowledged that Prader-Willi Syndrome has existed for centuries. A painting entitled ‘La Monstrua’ in the Museo del Prado in Spain is almost certainly that of little girl with PWS, and Langdown Down, who gave his name to Down’s Syndrome, also wrote a report of a woman with features which fit the PWS characteristics (Ward 1997).

PWS occurs in all races and in both sexes. It is rarely hereditary, can occur in any family, but rarely occurs more than once in a family. Several cases of non-identical twins have been reported, where one twin has PWS and the other does not; more rare are identical twins with PWS. As far as is known, PWS is purely accidental, and no blame can be attached to either parents or doctors.

The true incidence is not known, but is estimated to be 1:15,000, based on calculations made in the USA and Norway. Previously, life expectancy was believed to be short, as it was thought that massive obesity in the early years of life could not be avoided. Now, with better management, people are living well into middle age. The oldest recorded person in the UK was aged 71 when she died (Carpenter 1994). However, without considerable effort on the part of all who live and work with individuals with PWS, death at a very early age still remains a threat.

The genetic background

The genetics of PWS are quite complicated. It can be caused by more than one type of genetic abnormality, but all result in an important piece of genetic coding being missed from the paternal chromosome 15.

The most common genetic abnormality, which is present in about 70 per cent of people with PWS, is called a deletion. This means that a minute piece of chromosome 15 inherited from the father is missing, probably damaged around the time of conception. It is thought that the missing piece contained several genes, some of which have now been identified. However, experts are still uncertain which genes, or rather the lack of information contained in them, are instrumental in causing PWS.

Another form of genetic anomaly is known as maternal disomy, and is present in around 25–30 per cent of people with PWS. It occurs when two chromosome 15s are inherited from the mother, and none from the father. Again, important genetic coding material is missing because of the absence of the paternal genes. Interestingly, where the situation is reversed, and the chromosome deletion is on the maternal chromosome, or two paternal chromosomes are present, an entirely different syndrome results. This is Angelman Syndrome, which causes severe learning difficulties and a range of severe physical disabilities. It manifests very differently to Prader-Willi Syndrome.

In a few other rare cases, translocations and other rare anomalies occur, which are the only hereditary cases of PWS.

There appear to be few differences between those who have deletion and disomy. However, researchers have found that those with deletion are more likely to have the typical PWS facial features and lighter hair and skin colouring than those with disomy. Skin picking, articulation abnormalities and a high pain threshold are also more likely in those with deletion (Cassidy et al. 1995), and research is still going on to identify other differences.

It is widely thought that most of the genetic information which is missing in PWS affects the hypothalamus, which controls and regulates many of the body’s hormone mechanisms.

Diagnosis

The diagnosis of PWS has improved in recent years, partly because of increased awareness on the part of doctors, but also because chromosome tests are now done at a molecular level, and are therefore more able to detect the very small genetic anomalies which are present in PWS. Diagnosis is also carried out at the clinical level, which takes into account the various physical and mental characteristics of the child. There is still a very small minority of people who have most of the PWS characteristics but for whom no genetic anomaly can be found. These are often referred to as having ‘atypical PWS’. There are also people who have some form of brain damage, either through disease or injury, which results in PWS-like characteristics. The management techniques which are appropriate for people with ‘true’ PWS are also appropriate for these groups.

An early diagnosis is very important, so that behaviour and dietary management can become part of the child’s everyday life. However, some children do not receive a diagnosis until they are quite old – sometimes not until they are adults – and this can be very difficult for them and their parents to come to terms with. There are undoubtedly children who remain undiagnosed. If there is a suspicion the child has PWS, then they should be referred to a geneticist. Diagnostic criteria have been published (Holm et al. 1993) and are also available from the PWSA (UK).

Major physical characteristics

Hypotonia (low muscle tone)

Hypotonia is evident from birth, when babies usually present as very ‘floppy’. As they have poor sucking ability, they can be very difficult to feed, and often need tube-feeding. This has implications in later life for possible speech problems. Low muscle tone continues throughout life, but can be helped with appropriate exercise, which also has a positive impact on weight control. Researchers are beginning to find that growth hormone treatment has a very beneficial effect on muscle tone in PWS (Eiholzer et al. 1998).

The low muscle tone varies in degree between individuals, but some may find holding a pencil difficult and most will have difficulty running, jumping and generally keeping up with their peers. Some children will be walking by the time they are two years old, others may still be having difficulty at the age of five or older.

Hypogonadism (immature sexual development)

Hypogonadism is more obvious from an early age in males than females. However, both sexes are likely to experience delayed or arrested puberty, and this has implications for sex education as well as peer relations.

Obesity

The tendency towards obesity, which can be life-threatening even in young children, is caused by an excessive appetite (hyperphagia, see below), coupled with a decreased calorific requirement owing to low energy expenditure levels. Obesity used to be considered an essential criterion for diagnosis of PWS, so prevalent was it amongst the PWS population; but with better parental management and medical guidance, more and more children with PWS are growing up who are not obese. This does not mean they will not become obese if controls are relaxed. It is a very careful balancing act to provide the individual with the necessary skills to maintain their weight at a reasonable level, and many are unable to do this at all without considerable outside intervention.

Typical facial characteristics

Many people with PWS, particularly those with a deletion, share certain facial characteristics, to the extent that a group of people together can look like brothers and sisters. These features include: a narrow forehead, ‘almond-shaped’ eyes with upward-slanting lower eyelids, and a down-turned mouth. Hair and skin colouring is often lighter than that of other members of the family.

Characteristics arising from hypothalamic dysfunction

The hormone-regulating properties of the hypothalamus affect growth, sexual development, appetite, and emotional control, all of which are affected in PWS.

Hyperphagia

Hyperphagia, or excessive appetite, is perhaps the most well-known feature of PWS. In contrast to the so-called ‘first-stage’ of the syndrome, where babies show little interest in feeding, sometime between the ages of two and five the interest in food begins to increase. However, it can vary considerably between individuals. While all will show a marked interest in food, a minority are relatively well able to control their food intake, whilst others will take every opportunity to access food. This may involve unacceptable behaviours such as rooting through waste-bins, stealing food from others’ plates or out of their pockets, eating frozen food or pet food, or stealing money to buy food. Many are able to control their eating in supervised situations, but are unable to do so in unsupervised situations.

This behaviour can be understood in the context of the fact that it appears that the mechanism which informs most people when they have had enough to eat is faulty in people with PWS, and they feel hungry for most of the time, thus constantly thinking about, or seeking out, food (Holland 1998). Researchers are still unsure whether the variation in eating behaviour is due to differences in damage to the hypothalamus, other hereditary factors, or general education and management – both of carers and people with PWS.

Short stature

Many children with PWS are considerably shorter than their peers, and often have small hands and feet. However, increasingly, children are being prescribed growth hormone treatment which can often help with growth, as well as muscle tone. Some parents have also reported increased alertness and improved behaviour while their children have been on growth hormone. The average height for an adult who has not had growth hormone treatment is around 4′10″ (145 cm) for women, and 5′2″ (155 cm) for men. There are a few people with PWS who are taller than this, especially if they come from tall families.

Somnolence, tiredness

Sleeping patterns are also regulated by the hypothalamus, and these are often affected in people with PWS. As babies, they sleep for far longer than other babies, and can be difficult to rouse, even to feed. Young children require more naps, and even adults are prone to daytime sleepiness. This can be exacerbated by obesity. Sleep apnoea (cessation of breathing for short periods whilst asleep) can also interrupt sleeping patterns and, whilst this is more common in those who are obese, it has been noted in some children who are not. Researchers have also found evidence of unusual sleep patterns in individuals with PWS (Vela-Bueno et al. 1984).

Emotional instability

Individuals with PWS appear to have delayed or arrested emotional development, many exhibiting behaviours such as acting out, temper, tantrums, and stubbornness. These are charactistics which are normally evident in children of pre-school age but remain with the person with PWS all their life. Again, the degree to which this manifests varies considerably between one individual and another.

Other medical abnormalities sometimes associated with PWS

People with PWS do not always have the same medical reactions as most people. It is important that medical staff and first aiders are aware of these.

Adverse reaction to drugs

Although more is becoming known about the effects of drugs which react on the central nervous system of people with PWS (e.g. tranquillizers), there are still concerns that there may be adverse effects. Drugs to treat severely challenging behaviour in children are more widely used in the USA than in the UK, but need careful monitoring. Often, lower dosages than normal are required.

Prolonged drowsiness after routine anaesthesia, or complications arising from anaesthesia

If a child requires a general anaesthetic for any reason, the hospital should be informed that the child has PWS, and it can then take appropriate steps to monitor anaesthetic treatment. It is not unusual for a child to be drowsy for up to 24 hours after receiving anaesthetics. Very rarely, other complications may occur.

Irregular body thermostat

The hypothalamus also controls the body’s internal temperature. This appears to be impaired in some people with PWS. Erratic behaviour and lethargy may become more pronounced in very hot or very cold weather, and it is important that the classroom temperature is neither too hot nor too cold. Normal childhood infections may induce a higher than normal temperature, sometimes resulting in fitting, but sometimes the temperature does not rise in response to sickness.

High pain threshold

Children with PWS may have an abnormal response to pain, which varies considerably between individuals. It is best to check with the parent or carer how each child reacts. Some will feel little or no pain, even with broken bones or stomach infections. Others may over-react to a small cut or graze, whilst ignoring the pain of a more serious illness. Some may complain of pain as an attention-seeking device. However, in the first place it is best to treat any complaint of pain seriously, as the child may have a serious illness or wound which needs treatment. One example is the child who was always ‘crying wolf’ about her illnesses, and was only listened to when she developed a lump in her stomach. It transpired that she had a blockage in her bowel (Waters 1991).

Easy bruising

Some children seem to bruise very easily, and because of the high pain threshold mentioned above, may be unable to say how the bruise came about. This has implications for allegations of physical abuse, and careful monitoring of the child’s activities and environment should be undertaken in order to see how the bruising is happening if this is a worry.

Lack of vomiting

Many children with PWS rarely vomit, if at all. This is probably caused by the low muscle tone. Thus, if vomiting occurs in those who rarely vomit, it may be a sign of very serious illness, and medical attention should be sought immediately. The lack of vomiting also has implications if the child has eaten something poisonous, has a stomach infection or illness affecting the digestive system. Again, medical treatment should be sought immediately.

Additional physical disabilities

Most children with PWS are generally healthy, ...