Prader Willi syndrome is a rare genetic disorder that results in a number of physical, mental and behavioral problems. A key feature of Prader-Willi syndrome is a constant sense of hunger that usually begins at about 2 years of age. Prader-Willi syndrome is a genetic disorder usually caused by deletion of a part of chromosome 15 passed down by the father.

There is no cure for Prader-Willi syndrome but many patients will benefit from a supervised diet. Some symptoms can be treated with hormone therapy.

People with Prader-Willi syndrome want to eat constantly because they never feel full (hyperplasia), and they usually have trouble controlling their weight. Many complications of Prader-Willi syndrome are due to obesity. Signs and symptoms that may be present from birth include:

• Poor muscle tone.A primary sign during infancy is poor muscle tone (hypotonic). 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 may be born with almond-shaped eyes, a narrowing of the head at the temples, a turned-down mouth and a thin upper lip.
• Poor sucking reflex.Infants may have a poor sucking reflex due to decreased muscle tone. Poor sucking makes feeding difficult and can result in failure to thrive.
• Generally poor responsiveness.A baby may seem unusually tired, respond poorly to stimulation, have a hard time waking up or have a weak cry.
• Underdeveloped genitals.Males may have a small penis and scrotum. The testicles may be small or not descended from the abdomen into the scrotum (cryptorchidism).

Other features of Prader-Willi syndrome appear during early childhood and remain throughout life, requiring careful management. These features may include:

• Food craving and weight gain.A classic sign of Prader-Willi syndrome is a constant craving for food, resulting in rapid weight gain, starting around age 2 years. Constant hunger leads to eating often and consuming large portions. Unusual food-seeking behaviors, such as hoarding food, or eating frozen food or even garbage, may develop.

• Poor growth and physical development. Underproduction of growth hormone can result in short adult height, low muscle mass and high body fat. Other endocrine problems may include underproduction of thyroid hormone (hypothyroidism) or central adrenal insufficiency, which prevents the body from responding appropriately during stress or infections.
• Cognitive impairment. Mild to moderate intellectual disability, such as issues with thinking, reasoning and problem-solving, is a common feature of the disorder. Even those without significant intellectual disability have some learning disabilities.
• Delayed motor development. Toddlers with Prader-Willi syndrome often reach milestones in physical movement — for example, sitting up or walking — later than other children do.
• Speech problems. Speech is often delayed. Poor articulation of words may be an ongoing problem into adulthood.
• Behavioral problems. Children and adults may at times be stubborn, angry, controlling or manipulative. They may throw temper tantrums, especially when denied food, and may not tolerate changes in routine. They may also develop obsessive-compulsive or repetitive behaviors, or both. Other mental health disorders, such as anxiety and skin picking, may develop.
• Sleep disorders. Children and adults with Prader-Willi syndrome may have sleep disorders, including disruptions of the normal sleep cycle and a condition in which breathing pauses during sleep (sleep apnea). These disorders can result in excessive daytime sleepiness and worsen behavior problems.
• Other signs and symptoms. These may include small hands and feet, curvature of the spine (scoliosis), hip problems, reduced saliva flow, nearsightedness and other vision problems, problems regulating body temperature, a high pain tolerance, or a lack of pigment (hypo pigmentation) causing hair, eyes and skin to be pale.

CAUSES

Prader-Willi syndrome is a genetic disorder, a condition caused by an error in one or more genes. Although the exact mechanisms responsible for Prader-Willi syndrome haven’t been identified, the problem lies in the genes located in a particular region of chromosome 15.With the exception of genes related to sex characteristics, all genes come in pairs — one copy inherited from your father (paternal gene) and one copy inherited from your mother (maternal gene). For most types of genes, if one copy is “active,” or expressed, then the other copy also is expressed, although it’s normal for some types of genes to act alone.Prader-Willi syndrome occurs because certain paternal genes that should be expressed are not for one of these reasons:

• Paternal genes on chromosome 15 are missing.
• The child inherited two copies of chromosome 15 from the mother and no chromosome 15 from the father.
• There’s some error or defect in paternal genes on chromosome 15.

In Prader-Willi syndrome, a defect on chromosome 15 disrupts the normal functions of a portion of the brain called the hypothalamus, which controls the release of hormones. A hypothalamus that isn’t functioning properly can interfere with processes that result in problems with hunger, growth, sexual development, body temperature, mood and sleep.In most cases, Prader-Willi syndrome is caused by a random genetic error and is not inherited. Determining which genetic defect caused Prader-Willi syndrome can be helpful in genetic counseling.

TREATMENT

• Muscle weakness is a serious problem among individuals with Prader Willi Syndrome. For children younger than age 3, physical therapy may increase muscular strength and help such children achieve developmental milestones. For older children, daily exercise will help build lean body mass.

• Behavioral therapy. People with PWS have difficulty controlling their emotions. Using behavioral therapy can help. Stubbornness, anger, and obsessive-compulsive behavior, including obsession with food, should be handled with behavioral management programs using firm limit-setting strategies. Structure and routines also are advised. .
• Early interventions/Special needs programs. Individuals with Prader Willi Syndrome have varying degrees of intellectual difficulty and learning disabilities. Early intervention programs, including speech therapy and occupational therapy for delays in acquiring language and for difficulties with pronunciation, delayed milestones should begin as early as possible and continue throughout childhood.