Prader-Willi: cryptorchidism- shortness of stature- obesity- subnormal mentality; Prader-Willi Labhart

Prader-Willi syndrome is characterised by two phases. At birth and in infancy, hypotonia, sleepiness and feeding difficulties are usually present. Thereafter, hypotonia becomes less, feeding difficulties stop and hyperphagia (over eating) begins, usually between the ages of two to four.

Other features of Prader-Willi syndrome include:

• Hypogonadism (undescended testicles in males, reduced or lacking menstruation in females);
• mild to moderate intellectual disabilities;
• obesity (in the absence of food restrictions this appears to be universal).

The syndrome often includes:

• short stature;
• developmental delay in walking and speech;
• obsessive behaviour;
• strabismus (squint);
• almond-shaped eyes;
• very small hands and feet;
• skin picking;
• scoliosis;
• diabetes;
• behavioural problems.

Inheritance patterns
Prader-Willi syndrome is due to the loss of expression of maternally imprinted (paternally expressed) genes on the chromosome 15 of paternal origin. In approximately seventy per cent of cases this is due to a deletion, 15q11-q13, and in most other cases both copies of chromosome 15 are maternal in origin (maternal disomy) with no paternal copy. Rarely, it will arise as a result of a chromosomal translocation or a mutation in the imprinting centre, which may be transmitted through unaffected carriers. Genetic testing is undertaken using DNA and parental blood samples may be requested to confirm maternal disomy.

Prenatal diagnosis
Usually none at present. There may be reduced fetal movement. In the very rare known carrier families, amniocentesis may be recommended.

Medical text written November 1991 by Contact a Family. Approved November 1991 by Professor M Patton, Professor of Medical Genetics, St Georges Hospital Medical School, London, UK and Dr J E Wraith, Consultant Paediatrician, Royal Manchester Children's Hospital, Manchester, UK. Psychological and behavioural characteristics written November 1998 by Dr O Udwin, Consultant Clinical Child Psychologist, Society for the Study of Behavioural Phenotypes. Medical text last updated November 2004 and Psychological and behavioural characteristics last reviewed November 2004 by Dr J Whittington, Senior Research Associate, Section of Developmental Psychiatry, Department of Psychiatry, University of Cambridge, Cambridge, UK.

Psychological and behavioural characteristics

Prader-Willi syndrome is characterised by a number of distinctive psychological and behavioural features. Motor and language development are significantly delayed, and there are difficulties with gross motor skills, co-ordination and balance, voice problems (primarily hypernasality) and multiple articulation errors resulting in reduced intelligibility. These speech production problems are likely to be due at least partly to the early hypotonia and also the facial abnormalities associated with the syndrome. Spoken language is often considerably poorer than comprehension of language. Overall, cognitive abilities range from moderate learning difficulties through borderline abilities to average abilities or better, but usually with multiple learning disabilities. Severe learning difficulties are not commonly found.

The children tend to have an unusual cognitive profile, with particular strengths in visual organisation and perception, and in academic achievement tasks such as reading and vocabulary. Unusual skill with jigsaw puzzles is often noted. In contrast, auditory information processing and sequential processing are relatively weak, and most individuals have specific difficulties with arithmetic, writing, visual and auditory short-term memory and auditory attention.

Behaviourally, children with Prader-Willi syndrome tend to be floppy, sleepy and passive in the first year. Their muscle tone begins to improve towards the end of the first year and they become more active and alert. They are often described as easy-going, friendly and affectionate; but behavioural difficulties become increasingly apparent and severe with age. These are often related to the insatiable desire to obtain food, which develops between one and four years of age and is accompanied by excessive or rapid weight gain, and is physically, emotionally and socially debilitating. Excessive intake of food may cause life-threatening obesity and often involves foraging for food, stealing and hoarding food. Research shows that people with Prader-Willi syndrome think a lot more about food than other people, and may continue to eat at a steady rate as long as food is available.

Dietary management is the corner stone of managing the obesity. Typically, carers have to limit access to food and take over total control of food intake. Behaviour modification methods which rely on reinforcement and self-monitoring as part of weight control and exercise programmes, are also required. Long-term maintenance of weight loss is difficult to achieve, and problems with weight control can become worse in adult life when, with increased independence, food is more readily available.

Outbursts of rage and aggression, stubbornness and belligerence, are common in affected individuals, beginning around age three to five, becoming more marked later in childhood and persisting into adulthood. Tantrums and aggression may be related to wanting access to food, but typically extend also to situations unrelated to food (for example in response to changes in routine), and may occur with little provocation. Between the episodes of difficult behaviour, individuals with Prader-Willi syndrome are usually described as being good natured, placid and co-operative. They may be over friendly, with impulsive chatter, but most are also reported to be immature and socially isolated. Compulsive/obsessive behaviours and anxiety-based difficulties, excessive worry, and self-injury by deliberately picking or scratching the skin, are further common difficulties. The above behaviours are believed to result from the combination of the physical aspects of the syndrome, the relentless hunger, and the psychosocial pressures of being obese, sexually immature and cognitively limited. Physical inactivity and passivity are commonly reported, as are various sleep disorders, for example frequent waking in the night due to breathing difficulties (sleep apnoea) and excessive daytime sleepiness. In addition, psychiatric symptoms such as hallucinations, paranoia, agitation, anxiety and depression have been described in some adolescents and adults with the syndrome.

Further Online Resources
Medical texts in The Contact a Family Directory are designed to give a short, clear description of specific conditions and rare disorders. More extensive information on this condition can be found on a range of reliable, validated web sites and links to them are included in the CD-ROM version of this Directory. Further information on these resources can be found in our Medical Information on the Internet article.

PRADER-WILLI SYNDROME ASSOCIATION (UK)

Prader-Willi Syndrome Association (UK)
125a London Road
Derby DE1 2QQ
Tel: 01332 365676
Fax: 01332 360401
e-mail: admin@pwsa-uk.demon.co.uk
Web: http://www.pwsa.co.uk

The Association is a National Registered Charity No. 284583, established in 1981. It offers support, advice and contact with others. It organises multi-disciplinary training days for professional workers from health, education, social services and residential and community care. Local and regional group meetings are sometimes organised. It publishes a quarterly newsletter and has a wide range of information available, details on request. The Association has over 800 family members, over 200 adult members with Prader-Willi syndrome and over 800 professional members.

Group details last updated May 2007.