Q: Is there a disease some kids are born with that makes them want to eat all the time?

A: Prader-Willi Syndrome is a rare genetic condition, affecting about one in 25,000 live births. It is a sporadic disease (so typically not inherited, it occurs for unknown reasons), due to a problem with some of the genes on the proximal arm of chromosome 15. The genes involved are ones that are “imprinted,” meaning that the gene from one parent is differentiated from the gene from the other parent by being “marked” as the one that will be expressed (so the gene from the other parent cannot act as a “backup” copy for the baby if the gene from the "imprinted" parent mutates or is defective). In PWS the genes in question are imprinted so only the father’s genes are expressed; a mutation there can manifest as disease even if the mom’s genes are not mutated and are normal.

The abnormal genes in PWS manifest as multiple different symptoms. In infancy, babies with PWS often have decreased muscle tone (hypotonia, sometimes called "floppy baby" syndrome), occasionally so severe it can compromise breathing and/or feeding (due to decreased ability to nurse). They may have a weak cry, and possibly abnormal development of sexual organs (PWS affects both sexes, so the abnormal development can be in the testes/scrotum or vaginal tissue). Other symptoms may include lack of pigmentation of the skin and/or eyes.

By early childhood PWS patients usually fail to meet normal motor developmental milestones and will have increased appetite and eating (eventually leading to obesity). The child may not meet growth milestones (short stature is common secondary to growth hormone deficiency). Other developmental issues, including behavior disorders, intellectual impairment and other psychosocial issues may be noted. Seizures are common, occurring in up to one in four PWS patients. Choking on food is more common in PWS patients (family members should all be taught the Heimlich maneuver).

Adolescence is typically marked by early development of pubic and axillary hair but absent or delayed puberty, and delayed development of sexual characteristics (late testicular development in boys, and late breast development and/or menarche in girls). Pronounced increase in eating (hyperphagia) and subsequent obesity, due to the patient’s inability to feel "full" no matter how much they eat, is common at this age.

Complications related to PWS, often related to hormonal issues, obesity or other manifestations of the condition, are quite common. These may include early atherosclerotic heart disease, behavioral problems, orthopedic issues, sleep apnea, diabetes, dementia and other secondary complications. These complications often limit the patient’s lifespan. In addition, gastrointestinal problems and other complications may occur.

Since PWS patients always feel hungry, they often develop abnormal food-seeking behavior, such as eating garbage, frozen foods or stealing (food or other resources to allow them to buy food). In addition, their pain threshold and nausea/vomiting threshold are often blunted, which increases the likelihood of the abnormal food-seeking behavior.

The diagnosis of PWS is suspected in patients who meet certain criteria, scoring at least five points for kids under age 3 or eight points for those over age 3. The points come from the patient having at least three to four major criteria of one point each (neonatal hypotonia, feeding problems, certain physical characteristics, certain behavioral/intellectual abnormalities, and hyperphagia) plus a half point each from minor criteria (decreased fetal movement, feeding problems at birth, excess weight gain after infancy, sleep issues, short stature, decreased skin/eye pigmentation, as well as other criteria).

A diagnosis of PWS is confirmed with specific genetic testing. Other tests to look for complications (such as blood tests for growth hormone level, as well as other blood tests for other hormone levels, and possible imaging tests to look for osteoporosis, and even a brain MRI) may be indicated.

Care for PWS patients centers around limiting access to food (to minimize obesity and diseases it may cause), and other supportive care (including counseling, treatment of conditions that develop, etc.). Vigilance to identify and address possible complications early is important. Vocational programs, as well as occupational therapy as indicated, may be beneficial in some patients.

PWS is a lifelong condition that needs ongoing care. The Prader-Willi Syndrome Association at info@pwsausa.org is a great resource for patients and their families.
