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Prader-Willi Syndrome

Chromosome 15 disorder


Updated August 07, 2006

Prader-Willi syndrome is caused by a genetic disorder of chromosome 15. Prader-Willi occurs in approximately one of every 12,000-15,000 people, in both boys and girls, and in people of all ethnic backgrounds. Prader-Willi syndrome is usually diagnosed by the appearance and behaviors of a child, then confirmed by specialized genetic testing of a blood sample. Although rare, Prader-Willi syndrome is the most common genetic cause of obesity.

Two different stages of symptoms
At first, an infant with Prader-Willi syndrome will have trouble growing and gaining weight (failure to thrive). Because of weak muscles (hypotonia), the infant is not able to drink from a bottle, and may need special feeding techniques or tube feedings until his/her muscles become stronger. Infants with Prader-Willi syndrome are often behind other children in development.

Between ages 1-6 years the child with Prader-Willi syndrome suddenly develops a tremendous interest in food, and starts overeating. It is believed that the child with Prader-Willi never feels full after eating, and may actually go on eating binges. Parents of children with the syndrome often have to lock the kitchen cabinets and refrigerator to restrict the child's access to food. Children gain weight rapidly at this age.

Rate of growth slows
In addition to overeating, the child with Prader-Willi stops growing at a normal rate. The child gradually becomes short for his/her age, and because of overeating becomes excessively overweight.

Children with Prader-Willi syndrome have endocrine problems including reduced or absent secretion of sex hormones (hypogonadism) and delayed or incomplete sexual development. Children with the syndrome may also have mild to moderate mental retardation or learning problems, and may have behavior problems such as obsession, compulsion, stubbornness, and temper tantrums.

Distinctive facial features
Distinctive facial features also identify a child with Prader-Willi syndrome. These include a narrow face, almond-shaped eyes, small-appearing mouth, a thin upper lip with downturned corners of the mouth, and full cheeks. The child's eyes may cross (strabismus).

There is no cure for Prader-Willi syndrome. However, the physical problems caused by the syndrome can be managed. During infancy, special feeding techniques and formulas can help the infant grow. Physical therapy and exercise helps improve strength and coordination. Administering human growth hormone (Genotropin, Humatrope, Norditropin) improves muscle mass and growth.

Speech therapy can help children who are behind in their language skills to catch up to their peers. Special education services and supports help children with Prader-Willi achieve their full capacity.

As the child grows, eating and weight problems can by controlled through a balanced, low-calorie diet, weight monitoring, external food restriction, and daily exercise.

National Organization for Rare Disorders. Prader-Willi Syndrome.
- Prader-Willi Syndrome Association (USA). Frequently Asked Questions About Prader-Willi Syndrome.
- Scheimann, A. (2006). Prader-Willi Syndrome. eMedicine, accessed at http://www.emedicine.com/ped/topic1880.htm

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