PRADER-WILLI SYNDROME (PWS)
Ann Aspinall(UK)

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What is PWS?

PWS is a genetic condition with unusual behavioural characteristics (Roof et al, 2002). The characteristic symptoms and behaviours of PWS were first identified by Prader, Willi and Labhart in 1956 (Prader et al, 1956).

PWS is characterised by hyptonia and feeding problems in infancy, hypogonadism, characteristic facial problems, short stature, developmental delay, obesity and an obsession with food and eating (Richdale et al, 1999)

Most people with PWS have mild intellectual disabilities (mean IQ 60s to 70s), with approximately 40% having borderline learning disabilities and about 20% having moderate intellectual disabilities. Regardless of measured IQ, most children with PWS have multiple severe intellectual disabilities, and their academic performance is poor for their mental abilities.

New born baby

• Usually small, weak and floppy with feeble cry
• Poor or no suck, leading to feeding problems
• Reflexes which are usually present at birth may not appear until later
• Physical feature may include: narrow face, almond shaped eyes, small mouth, feet and hands, fair skin and hair and small genitalia (more apparent in male babies)

Early infancy

• During the first year of life, the degree of floppiness reduces and motor functions begin to improve (although they are likely to remain delayed or weak)
• Most infants will sit, stand and walk late
• Muscle tone is likely to cause later problems with speech
• A wide range of IQ (mean of 70;some have SID and others IQs approaching 100)
• Most display a degree of stubbornness (frequently associated with food issues)
• Generally placid, cheerful and affectionate babies

Late infancy

• Most are better at concrete, rather than abstract, concepts (e.g. jigsaw puzzles/wordsearch)
• Preoccupation with food: This can be lessened by good management and strict dietary control but if not monitored weight gain is rapid
• In many ways food becomes central to their lives as they enjoy:
  • Thinking about it
  • Talking about it
  • Looking at it
  • Preparing it
  • And most of all, eating it

   

Weight gain in infancy

• Infants are slow to put on weight
• Between the ages of 2 and 4 their appetite increases dramatically (believed to be due to hypothalamic abnormality resulting in lack of satiety
• They consume everything that is put in front of them (hyperphagia)
• This is the beginning of a life-long problem

This weight gain is not due to just excessive food intake, but also the need for fewer calories that the norm to maintain an acceptable weight. Thus there is a combination of seemingly insatiable appetite and a reduced biological need for food.

Primary years

Problems which may begin to appear include:

• Perseveration
• Temper tantrums
• Obsessive and compulsive behaviour
• Stubbornness
• Rigidity
• Skin picking
• Many have poor auditory processing

Teenage years

• Puberty is usually delayed and incomplete in both sexes
• Infertility
• Tendency to be shorter in height (compared to other family members)
• The risk of scoliosis is increased
• Social Skill deficiencies become even more apparent

Adulthood

• All problems from childhood remain, especially those relating to food
• Sleep problems/sleep apnea
• Life expectancy has increased in recent years but few individuals live into their forties

Interventions

• Professionals should be involved at an early age:
  • Paediatricians, health visitors, portage workers, physiotherapists, psychologists, speech therapists, dentists, opticians and dietitians
• Educational intervention is also considered to address cognitive, physical and other developmental delays
• Exercise to improve poor muscle tone
• Children should be taught to recognise a sensible portion size
• Visual aids and cues to learning should be used because of poor auditory processing
• Children should be reassured about times
• Children should be given limits as to how long they can go on repeating questions
• Strategies for coping with change in routine should be taught
• Assistance in making simple choices
• Growth hormone deficiency may require referral to an endocrinologist
• Repeated revision and consolidation is necessary (because of poor short term memory)
• Many find it difficult to work in groups but make progress in 1:1 situations

Genetic information

Prevalence

The estimated prevalence of PWS is 1 in 10,000 to 1 in 15,000 (Burd et al, 1990)

Recurrence Risk

In the vast majority of cases, the risk of having another child with PWS is very slight indeed.

Genetics

Current research has shown that PWS results mainly from one of four genetic abnormalities:

1. A small deletion of Chromosome 15
2. Chromosome 15 maternal disomy
3. A translocation of chromosome involving Chromosome 15
4. An error in the imprinting of Chromosome 15

Clinical diagnosis

Consensus diagnostic criteria for PWS developed in 1993 (Holm et al) have proven to be accurate (Cassidy, 1997)

Burd, L., Vesely, B., Martsolff, J. & Kerbeshian, J. (1990). Prevalence study of Prader-Willi syndrome in North Dakota. American Journal of Medical Genetics, 37, pp 97-99

Cassidy, S.B. (1997). Prader-Willi syndrome. Journal of Medical Genetics, 34, PP 917-23

Holm, V.A., Cassidy, S.B., Butler, M.G., Hanchett, J.M., Greenswag, L.R., Whitman, B.Y. & Greenberg, F. (1993). Prader-Willi syndrome: consensus diagnostic criteria. Pediatrics, 91, PP 398-402

Prader, A., Labhart, A. & Willi, H., (1956). Ein Syndrom vom Adipositas, Kleinwuchs Kryptorchismus und Oligophenie nach myatonieartigem Zustand im Neugeborenalter. Schweizerische Medicinische Wochwenschrift, 86, 12601

Richdale, A.L., Cotton, S. & Hibbit, K. (1999). Sleep and behaviour disturbance in Prader-Willi syndrome: a questionnaire study. Journal of Intellectual Disability Research, Vol 43, (5), PP 380-392

Roof, E., Stone, W., MacLean, W., Feurer, I.D., Thompson, T. & Butler, M.G. (2000). Intellectual characteristics of Prader-Willi syndrome: comparison of genetic subtypes. Journal of Intellectual Disability Research, Vol 44 (1) PP 25-30

Websites:

Prader-Willi Syndrome Association (UK): www.pwsa-uk.demon.co.uk

GeneClinics: www.geneclinics.org

This article was first published on the site in 2002.

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