Signs and symptoms of Prader-Willi syndrome generally occur in two stages. Signs of the disorder that may be present in the first year of life include:
- Poor muscle tone. A primary sign of Prader-Willi syndrome during infancy is poor muscle tone (hypotonia). Babies may rest with their elbows and knees loosely extended instead of fixed, and they may feel floppy or like "rag dolls" when they're held.
- Distinct facial features. Children with Prader-Willi syndrome may be born with almond-shaped eyes, a narrowing of the head at the temples, a turned-down mouth and a thin upper lip.
- Failure to thrive. During the first year of life, children with Prader-Willi syndrome may have a poor sucking reflex due to decreased muscle tone. Because poor sucking makes feeding difficult, they tend to gain weight slowly.
- Lack of eye coordination (strabismus). The eyes of a child with Prader-Willi syndrome may not move together. Therefore, they may cross or wander to the side.
- Generally poor responsiveness. A baby may seem unusually tired, respond poorly to stimulation, wake with difficulty or have a weak cry.
From about ages 1 to 4, other signs of Prader-Willi appear. These problems will remain present throughout life and require careful management or treatment. These signs may include:
- Food craving and weight gain. The classic signs of the disorder are a constant craving for food and a rapid gain in weight. Because a child with Prader-Willi syndrome is always hungry, he or she eats frequently and consumes large portions. A child may develop unusual food-seeking behaviors, such as hoarding food or eating things such as garbage or frozen food.
- Underdeveloped sex organs. A condition called hypogonadism occurs when sex organs — the testes in men and the ovaries in women — produce little or no sex hormones. This results in underdeveloped sex organs, incomplete development at puberty and in nearly all cases infertility. Women may not start menstruating until their 30s, or they may never menstruate. Men may not have much facial hair, and their voices may never fully deepen.
- Poor growth and physical development. Children with Prader-Willi syndrome have low muscle mass. They may have short hands and feet. When a person with the disorder reaches full adult stature, he or she is usually shorter than other family members.
- Learning disabilities. Mild to moderate cognitive impairment is a common feature of the disorder. Essentially all people with Prader-Willi syndrome, even those without significant cognitive disability, have some learning disabilities.
- Delayed motor development. Toddlers with Prader-Willi syndrome often reach milestones in physical movement later than do other children. Sitting up by oneself may be delayed until 12 months and walking until 24 months.
- Speech problems. Speech is often delayed until a child is 2 years of age. Poor articulation of words may be an ongoing problem.
- Behavioral problems. Children may at times be very stubborn or throw temper tantrums, especially when denied food. They may also develop obsessive-compulsive disorder, which results in unwanted, recurring thoughts or repetitive behaviors, or both. Other mental health disorders, such as skin picking or rectal gouging, may develop.
- Sleep disorders. Some children with Prader-Willi syndrome may have sleep disorders, including disruptions of the normal sleep cycle and sleep apnea, a condition in which breathing pauses during sleep. Obesity may worsen sleep disorders.
- Scoliosis. A number of children with Prader-Willi syndrome develop abnormal curvature of the spine (scoliosis).
Other signs and symptoms of Prader-Willi syndrome may include:
- Nearsightedness (myopia)
- Light skin compared with other family members
- High pain tolerance
When to see a doctor
A number of conditions can cause some of the early signs of Prader-Willi, such as a failure to thrive, poor muscle tone and poor sucking. Therefore, it's important to get a prompt and accurate diagnosis.
See your doctor if your infant:
- Has difficulty feeding
- Doesn't wake easily
- Doesn't respond to touch
- Has rag doll-like limbs
See your doctor if your older child shows any of the following signs:
May. 01, 2013
- Rapid weight gain
- Constant hunger
- Unusual food-seeking behaviors
- Cassidy SB, et al. Prader-Willi syndrome. European Journal of Human Genetics. 2009;17:3.
- Prader-Willi syndrome. Genetics Home Reference. National Library of Medicine. http://ghr.nlm.nih.gov/condition/prader-willi-syndrome/show/print. Accessed Feb. 23, 2011.
- Scheimann AO. Clinical features, diagnosis, and treatment of Prader-Willi syndrome. http://www.uptodate.com/index.html. Accessed Feb. 15, 2011.
- McCandless SE, et al. Health Supervision for Children With Prader-Willi Syndrome. Pediatrics. 2011;127:195.
- Cassidy SB, et al. Prader-Willi Syndrome. In: Pagon RA, et al., eds. GeneReviews. Seattle, Wash.: University of Washington; 1993. http://www.ncbi.nlm.nih.gov/books/NBK1330/. Accessed Feb. 23, 2011.