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Prader-Willi syndrome


ICD-10: Q87.1F

ORPHA: 739

General information

Estimated occurrence
6-8:100,000 live births.

The syndrome is caused by several different types of abnormalities on chromosome 15, in most cases 15q11-13. These abnormalities lead to abnormal development of the brain and the hypothalamus, which in turn affects several bodily functions.

General symptoms

Distinctly poor muscle tone (hypotonia) occurs from birth and is due to muscle weakness and reduced muscle mass. Nursing difficulties are common during the first year. At age 2–4 a weight increase occurs despite normal energy intake. Individuals with Prader-Willi syndrome (PWS) develop an obsession with food, often around the age of 5, with an insatiable appetite. This has to be controlled with a strict diet in order to avoid a life-threatening weight gain. Without early treatment, the child often develops extreme obesity, with increased risk of Type 2 diabetes, cardiovascular disease, and short stature. Since the early 2000s, children with PWS are given growth hormones from the age of 3–6 months, which has altered the range of symptoms. Short stature is unusual today. Hormone treatment combined with a restrictive diet has reduced obesity among young people with PWS, and the risk of complications at an adult age is probably lower.   

Commonly occurring symptoms include dysfunctional breathing and an increased risk of breathing difficulties, particularly in combination with respiratory tract infections. Narrowed respiratory tracts can lead to snoring and sleep apnea. Disrupted temperature regulation and a high pain threshold are common, as is acid reflux. Many people with PWS react atypically to medication (opiates, sedatives) and anaesthetic gases. Epilepsy may occur. Scoliosis and osteoporosis are common. Sores and bruises may occur due to pinching/scratching of the skin, also known as skin picking. Many young people with PWS have delayed pubertal development, requiring sex hormone supplements. Motor development is often delayed. Intellectual development varies – most commonly there is a mild to semi-severe intellectual impairment. Moods swings and behavioural disorders are common, and about a third of people with PWS have an autism spectrum disorder.

Orofacial/odontological symptoms

About 25% of all people with PWS lack one or several tooth germs. Enamel defects and small teeth also occur. Many have a high-vaulted palate and irregular teeth or an irregular bite. People with PWS have reduced saliva production, and their saliva is often thick and sticky. There is an increased risk of caries due to eating disorders, enamel defects and dry mouth. However, a regulated diet can reduce the occurrence of caries in people with PWS. A different composition and reduced amount of saliva, in combination with reflux and bruxism, can contribute to rapid loss of tooth tissue.

Floppiness caused by weak muscles in newborn children mean that most infants with PWS cannot be breastfed – many require a special bottle or tube-feeding. Chewing difficulties and other oral motor problems are also common. Speech and language development are often delayed.

Advice on follow-up and treatment

  • Important that people with PWS receive dental attention and care at an early stage, for training, dietary information and reinforced preventive care.
  • Appropriate with a referral to specialist dental care in pediatric dentistry for an assessment.
  • Dry mouth should be monitored and saliva stimulation recommended.
  • Bruxism should be followed up and treated with a mouth guard.
  • Teeth and occlusion development should be monitored, and verifying tooth germ is important. In the event of abnormalities, an orthodontist should be consulted at an early stage in order to plan any occlusal correction treatment.
  • Sometimes sedation or anaesthetics are required in carrying out dental care. Consult a doctor due to increased occurrence of dysfunctional breathing and sensitivity to anaesthetic and sedative medication among PWS patients.
  • Oral motor training may be considered in the event of eating difficulties, limited facial expressions and drooling.
  • Speech, language and communication training are often warranted.


National Board of Health and Welfare Ågrenska's documentation Ågrenska's documentation - adult visit National care program, Prader Willi syndrome TAKO Senteret, Prader-Willi syndrom (PWS)

Updated: 2023-10-30 11:45