Syndromes: Prader-Willi syndrome

A series about conditions with common symptoms that constitute syndromes

A series about conditions with common symptoms that constitute syndromes

A series about conditions with common symptoms that constitute syndromes

Prader-Willi syndrome (PWS) described in 1956 by Prader, Labhart and Willi is often referred to as Prader-Labhart-Willi syndrome, PWS or Willi-Prader syndrome. It is a complex genetic disorder (Bar et al 2017) characterised by excessive obesity with individuals often weighing more than 200% of their recommended weight (Napolitano et al 2010).

A child with Prader-Willi syndrome

PWS affects both sexes equally across all races. Affected infants present with hypotonia and feeding difficulties resulting in poor weight gain, failure to thrive and sleepiness (Bar et al 2017, McCandless and The Committee on Genetics 2011). Between 12-18 months approximately, there is evidence of an insatiable appetite referred to as hyperphagia leading to obesity and characteristic behavioural difficulties (McCandless and The Committee on Genetics 2011). Other characteristics include short stature and hypogonadism. In some cases, a learning disability may be present.


PWS is caused by a genetic defect on chromosome 15 and most of the cases are not inherited. It is thought to affect approximately one in 10,000 to 30,000 people worldwide. Those presenting with PWS do not usually have a family history of the syndrome.

Associated health needs

PWS is the most common syndromal cause of obesity and complications associated with this are the primary causes of morbidity and mortality in patients with PWS (Angulo et al 2015).

Without adequate weight control and management programmes around food, significant increase of obesity-related health conditions can occur including diabetes, sleep apnoea, poor mobility and cor pulmonale. These increased health risks may reduce life expectancy with some individuals not surviving beyond their fourth decade. Yet, with appropriate behavioural management programmes, individuals with PWS can live well and healthy into their seventies (McCandless and The Committee on Genetics 2011).


Diagnosis of PWS should be considered if the infant presents with hypotonia, poor sucking reflex and feeding difficulties. In older children, insatiable appetite with rapid weight gain is another indicator for PWS testing. However, confirmation of the diagnosis should also include genetic testing. 

Treatment and support

Given that obesity is a factor leading to reduced life expectancy for people with PWS, it is critical that a behavioural management programmes around food is adopted from the initial diagnosis. Later, as children may often have a distorted body image associated with their obesity (Napolitano et al 2010), psychological as well as health assessments, evaluation and treatment must be considered.

Case study

Tom (not his real name) was a poor feeder from birth and was subsequently diagnosed with Prader-Willi syndrome (PWS). Tom is now ten and lives at home with his parents.

Tom’s poor body image because of his obesity is upsetting him, resulting in severe behavioural problems including seeking food, eating non-food items and stealing money to buy food. His parents are concerned and seeking support in terms of managing Tom’s behaviours.

While PWS needs to be managed from an early age the importance of behavioural management programmes particularly around food is critical. Health surveillance is also crucial to ensuring Tom’s life expectancy. Therefore, the importance of early intervention, positive behavioural supports and the input and support from the multidisciplinary team cannot be over-emphasised.


Further information

Prader-Willi Syndrome Association UK


Lynne Marsh is a senior lecturer at the School of Nursing and Midwifery, Queens University Belfast

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