15q Prader-Willi Syndrome

15q Prader-Willi Syndrome

If you have just found out through prenatal testing that your baby has or may have 15q Prader-Willi syndrome and are looking for more information, the Genetic Support Foundation is a good starting point. Below you will find information about this condition as well as a list of resources that can provide you with additional information and support. After reviewing the information below, if you have a question that you are having difficulty finding an answer for, please feel free to contact us. 

Overview of Important Information about 15q Prader-Willi syndrome

Prader-Willi syndrome is associated with a variety of health and developmental concerns. It is important to remember that each individual with Prader-Willi syndrome is unique. All individuals with Prader-Willi syndrome have some degree of developmental and intellectual disabilities. Intellectual disabilities tend to be on the mild end of the spectrum. Other common health concerns include obesity and infertility, and behavioral issues are also common.

What is life like for people with 15q Prader-Willi syndrome?

People with Prader-Willi syndrome can have loving relationships with friends and family, learn and make progress in their social skills and communication at their own pace. The majority of individuals with Prader-Willi syndrome are expected to need support and care over their lifetime given their disabilities and health concerns.

What Causes Prader-Willi syndrome?

There are several different types of rare genetic changes that can cause Prader-Willi syndrome. Each of these changes ultimately result in the loss of function of several genes on the paternally inherited (from the father) chromosome 15. As with most all of our genes, we inherit our genes in matched pairs: one copy from the egg of the mother and one copy from the sperm of the father. While a loss of function of these genes on chromosome 15 passed down specifically from the father causes Prader-Willi syndrome, there is nothing known at this time that a father could do to cause or prevent these genetic changes from occurring.  

Most of the time (about 70%), Prader-Willi syndrome is caused by a “de novo” deletion on the paternal copy of chromosome 15. This means that the deletion was not present in the father– it is unique to that individual. A “de novo” genetic change  is one that appears in the egg or sperm or in the early embryo and is then copied into all future cells of that individual. Prenatal screening tests using cfDNA may report a higher chance of Prader-Willi syndrome due the possibility of a deletion on chromosome 15.  

Prader-Willi syndrome can be also caused when an individual receives two copies of chromosome 15 from the mother (uniparental disomy) and therefore lacks the paternal copy of chromosome 15. This is the cause of Prader-Willi syndrome in about 25% of cases.

In rare cases, Prader-Willi syndrome can also be caused by a genetic change that inactivates genes on the paternal chromosome 15. These individuals inherited a paternal copy of chromosome 15, but because the paternal genes are inactive the individual will have Prader-Willi syndrome.

What are the Health and Developmental Concerns Associated with Prader-Willi syndrome?

Prader-Willi syndrome is associated with a variety of health and developmental concerns. Infants with Prader-Willi syndrome have difficulties with feeding, muscle weakness, and delayed growth and development. Young children with Prader-Willi syndrome begin to develop an uncontrollable appetite and many become obese, which may lead to diabetes in some individuals.  Intellectual impairment is common and usually on the mild end of the spectrum. Behavioral issues such as temper tantrums and compulsive behavior are also characteristic of Prader-Willi syndrome. Individuals with Prader-Willi syndrome have delayed or incomplete puberty, leading to infertility in most individuals with this syndrome.

If I have a baby with Prader-Willi syndrome, what is the chance I will have another baby with this condition?

The chance of having another baby with Prader-Willi syndrome depends on the type of genetic change that caused Prader-Willi syndrome in the individual. Prader-Willi syndrome caused by a deletion in the paternal chromosome 15 or by uniparental disomy are usually not inherited from the parent and have a less than 1% chance of happening again in future children. Prader-Willi syndrome caused by a mutation in the paternal chromosome 15 have up to a 50% chance of reappearing in future children when the genetic change was inherited from a parent. Genetic testing would be needed to find the cause of Prader-Willi syndrome and determine the risk to future children.

How do parents of children with Prader-Willi syndrome feel about raising a child with Prader-Willi syndrome?

A study that surveyed the parents of 110 school aged children with Prader-Willi syndrome reported that the majority of parents felt that their child had brought joy and happiness to their lives, they said they enjoyed their child’s sense of humor, and felt that having their child changed their outlook on life. Many parents indicated challenges regarding parenting a child with Prader-Willi syndrome related to aggressive behavior, obsessive behavior, and difficulty managing their child’s diet. In considering the future, concerns most frequently reported related to parents’ worries about their child’s ability to live independently, uncertainty about who would care for their child when the parents were gone, and concern about their child’s happiness and health.

What is the treatment for Prader-Willi syndrome?

There is no “cure” for Prader-Willi syndrome, however medical management can help individuals reach their full potential. Individuals with Prader-Willi syndrome will need regular follow-up and treatment by a variety of health specialists to treat their specific needs. Intervention programs such as physical, speech, and behavior therapy can be very beneficial to individuals with Prader-Willi syndrome. Individuals with Prader-Willi syndrome will need lifelong diet management to avoid the health complications of obesity.

What are the long-term outcomes for individuals with Prader-Willi syndrome?

It is important to recognize that the health and developmental effects of Prader-Willi syndrome vary from person to person. Improvement in behavioral issues, muscle weakness, and many other symptoms can be expected with intervention programs. Individuals with Prader-Willi syndrome have mild to moderate intellectual disabilities and will benefit from special education. People with Prader-Willi syndrome are expected to need care and support over their lifetime. Life expectancy for individuals with Prader-Willi is expected to be normal with good health management.

How common is Prader-Willi syndrome?

Prader-Willi syndrome is believed to affect between 1 in 10,000 and 1 in 30,000 people.

Other Resources

The Prader-Willi Syndrome Association  provides resources for support and education for families caring for an individual with Prader-Willi syndrome.

IPWSO provides resources for support and education for families caring for an individual with Prader-Willi syndrome.

The Foundation for Prader-Willi Research provides resources for education about Prader-Willi syndrome and funds research. 


Reilly C, Murtagh L, Senior J. The Impact on the Family of Four Neurogenetic Syndromes: A Comparative Study of Parental Views. J Genet Couns. 2015 Jan 19.

Online Mendelian Inheritance in Man, OMIM®. Johns Hopkins University, Baltimore, MD. MIM Number: 176270: 10/03/2016: . World Wide Web URL: https://omim.org/

Prader-Willli syndrome: National Library of Medicine (US). Genetics Home Reference [Internet]. Bethesda (MD): The Library; 2017 Jan 24. Angelman syndrome; [reviewed 2014 June; cited 2017 Jan 30]; [about 6 screens]. Available from: https://ghr.nlm.nih.gov/condition/angelman-syndrome

Driscoll DJ, Miller JL, Schwartz S, et al. Prader-Willi Syndrome. 1998 Oct 6 [Updated 2016 Feb 4]. In: Pagon RA, Adam MP, Ardinger HH, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2017. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1330/

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