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$Unique_ID{BRK04135} $Pretitle{} $Title{Prader-Willi Syndrome} $Subject{Prader-Willi Syndrome Prader-Labhart-Willi Fancone Syndrome Hypogenital Dystrophy with Diabetic Tendency HHHO Hypotonia-Hypomentia-Hypogonadism-Obesity Syndrome Cryptochidism-Dwarfism-Subnormal Mentality Labhart-Willi Syndrome Angelman Syndrome Cohen Syndrome Alstrom syndrome Laurence-Moon-Biedl Syndrome} $Volume{} $Log{} Copyright (C) 1984, 1985, 1987, 1988, 1989, 1992 National Organization for Rare Disorders, Inc. 14: Prader-Willi Syndrome ** IMPORTANT ** It is possible that the main title of the article (Prader-Willi Syndrome) is not the name you expected. Please check the SYNONYMS listing to find the alternate name and disorder subdivisions covered by this article. Synonyms Prader-Labhart-Willi Fancone Syndrome Hypogenital Dystrophy with Diabetic Tendency HHHO Hypotonia-Hypomentia-Hypogonadism-Obesity Syndrome Cryptochidism-Dwarfism-Subnormal Mentality Labhart-Willi Syndrome Willi-Prader Syndrome Information on the following diseases can be found in the Related Disorders section of this report: Angelman Syndrome Cohen Syndrome Alstrm syndrome Laurence-Moon-Biedl Syndrome General Discussion ** REMINDER ** The Information contained in the Rare Disease Database is provided for educational purposes only. It should not be used for diagnostic or treatment purposes. If you wish to obtain more information about this disorder, please contact your personal physician and/or the agencies listed in the "Resources" section of this report. Prader-Willi syndrome is a complex multisystem disorder diagnosed more often in males born after a prolonged gestation period (delayed birth), often in the breech position. This disorder is characterized by muscular weakness in the infant (infantile hypotonia), failure to thrive, a decrease in the efficiency of the testes or ovaries (hypogonadism), short stature and impaired intellectual and behavioral functioning. Hyperphagia (eating excessive amounts of food) leads to severe obesity in early childhood and adolescence. Symptoms Early symptoms of Prader-Willi syndrome include decreased fetal movement, low birth weight, muscular weakness (hypotonia), sleepiness, a weak cry and poor sucking ability. Other characteristics may include unusually small hands and feet (acromicria), narrow forehead (bifrontal diameter), crossing of the eyes (strabismus), almond-shaped eyes (palpebral fissures), and developmental delays relating to head control and the ability to crawl. A need to eat an extraordinary amount of food (hyperphagia) usually develops between 1 to 3 years of age. If left uncontrolled, the obesity of Prader-Willi Syndrome can lead to life-threatening heart and lung complications, diabetes, hypertension and to other serious disorders. The compulsion to eat is so overwhelming in people with this disorder that if left unsupervised, they may endanger themselves by eating inedible objects. The sexual development of children with Prader-Willi syndrome may begin earlier than normal but generally stops after puberty. In males the testes may fail to descend into the scrotum (cryptorchidism) and the penis may be very small (micropenis). Unusually small and underdeveloped (hypoplastic) labia are seen less frequently in girls. Patients are mentally retarded, most with IQ's between 40 and 60, but some patients can be only mildly retarded. Patients tend to have fair coloring, blue eyes and sun-sensitive skin. They may frequently scratch or pick at sores and insect bites. There are also behavioral symptoms associated with Prader-Willi Syndrome including temper tantrams which may become more severe during adolescence. Causes Prader-Willi Syndrome is a rare genetic disorder caused most frequently by a cytogenetic deletion of chromosome 15q11q13. The deletion always occurs on the chromosome from the father (paternally derived); these are sporadic (new and spontaneous or "de novo") deletions, since the father of the child affected with Prader-Willi syndrome has normal chromosomes. There is less than 1:1000 risk of recurrence when a cytogenetic deletion is found. Prader- Willi syndrome may be inherited as a dominant gene. Human traits including the classic genetic diseases, are the product of the interaction of two genes for that condition, one received from the father and one from the mother. In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed "dominating" the normal gene and resulting in appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child.) An identical cytogenetic deletion is seen in patients with Angelman syndrome, but the chromosome involved is always from the mother (maternal origin). These findings suggest that chromosomal imprinting may be critical in the expression of these two syndromes. Symptoms of Angelman syndrome are very different from the symptoms of Prader-Willi syndrome (see the related disorders section of this report). Some patients with Prader-Willi syndrome who do not have a cytogenetic deletion on chromosome 15 have been found (by the testing of genetic material, DNA markers) to have inherited both of their 15th chromosomes from the mother (maternal uniparental disomy). Uniparental disomy is a condition in which both chromosomes are inherited from the same parent, in this case the mother. In genetics, human traits are the product of two genes, one inherited from the father and one from the mother. Scientists do not understand why uniparental disomy occurs in some people. Additionally, an environmental cause of chromosome 15 abnormality has been proposed; namely, the prolonged exposure of the father to hydrocarbons but there is no evidence for chromosomal breakage caused by hydrocarbons. Affected Population Prader-Willi syndrome is a rare disorder found more often in males than females. Its prevalence is unknown since many patients with Prader-Willi Syndrome are undiagnosed or misdiagnosed. Related Disorders Symptoms of the following disorders can be similar to those of Prader-Willi syndrome. Comparisons may be useful for a differential diagnosis: Angelman Syndrome is a very rare genetic disorder characterized by severe mental retardation, unusual facial expression and muscular abnormalities. It was first described in the medical literature as the "happy puppet syndrome". Other symptoms usually include a small head (microcephaly), a protruding jaw (mandible) and an open mouth and visible tongue. Patients seem to smile continually and they laugh excessively. Speech is generally absent. The symptoms of Prader-Willi Syndrome are not similar to Angelman Syndrome but they are both caused by a similar defect on chromosome 15. (For more information on this disorder, choose "Angelman Syndrome" as your search term in the Rare Disease Database). Cohen Syndrome is a rare genetic disorder characterized by multiple facial, mouth and eye abnormalities, muscle weakness, obesity and mental retardation. Children who have Cohen syndrome usually have a low birth weight and delayed growth. Other symptoms of this disorder may include an usually small head (microcephaly), a high nasal bridge, an open mouth, prominent lips and large ears. The jaw may develop abnormally and there may be a mild down-slant to the eyes. (For more information on this disorder, choose "Cohen Syndrome" as your search term in the Rare Disease Database). Alstrm Syndrome is a rare inherited disorder characterized by retinitis pigmentosa (degeneration of the retina in the eyes) and childhood obesity. There is usually degeneration of the retina leading to visual impairment. Involuntary rhythmic movements of the eyes and the loss of central vision occur. The child generally develops hearing loss and diabetes mellitus after the age of ten. (For more information on this disorder, choose "Alstrm Syndrome" as your search term in the Rare Disease Database). Laurence-Moon-Biedl Syndrome is a rare inherited disorder characterized by a decrease in the efficiency of the testes or ovaries (hypogonadism), retinitis pigmentosa (degeneration of the retina in the eyes), mental retardation, more than the normal number of fingers or toes (polydactyly), and obesity. Obesity is one of the earliest signs of this disorder. (For more information on this disorder, choose "Laurence-Moon-Biedl Syndrome" as your search term in the Rare Disease Database). Therapies: Standard The treatment for Prader-Willi syndrome is symptomatic and supportive. High resolution prometaphase chromosome analysis is recommended to identify the specific genetic defect. Physical therapy may be necessary to help develop a proper walking pattern, and improve muscle size and tone. Exercise programs can be helpful for weight control. The development of a proper diet, good nutrition, and a good exercise program are necessary to deal with the life-threatening insatiable appetite of Prader-Willi patients. A highly structured residential program is usually necessary, keeping food out of reach of the patient. Meals must be calorie controlled containing approximately 60 percent less calories than would normally be expected. Therapies: Investigational Prader-Willi Syndrome is the subject of ongoing medical research including studies in the area of obesity and chromosomal abnormalities. Specific diets, studying behavior, daily hormone cycles and brain scans are also the subject of studies. For further information contact: NIH/National Institute of Child Health and Human Development (NICHD) 9000 Rockville Pike Bethesda, MD 20892 Att: Dr. Sidbury (301) 496-6683 Prader-Willi syndrome and its association with diabetes and nutrition are also under investigation. For further information contact: USC Medical Center 2025 Zonal Avenue, Rm. 252 Los Angeles, CA (213) 226-7616 Att: George Bray, M. D. The Prader-Willi Syndrome Association is funding a study on the molecular genetics of Prader-Willi patients. Interested parties may get more information by contacting: Drs. Suzanne Cassidy or Robert Erickson Dept. of Pediatrics University of Arizona Tucson, AZ Scientists are studying the use of Human Growth Hormone (hGH) in Prader- Willi Syndrome in the hope that the drug may decrease fat and build muscle. However, the drug is very expensive ($10,000 to $40,000 per yer) and some insurors will not pay for it unless there is proof that the patient has an actual deficiency of growth hormone. This disease entry is based upon medical information available through September 1992. Since NORD's resources are limited, it is not possible to keep every entry in the Rare Disease Database completely current and accurate. Please check with the agencies listed in the Resources section for the most current information about this disorder. Resources For more information on Prader-Willi Syndrome, please contact: National Organization for Rare Disorders (NORD) P.O. Box 8923 New Fairfield, CT 06812-1783 (203) 746-6518 Prader-Willi Syndrome Association 1821 University Ave., N-356 St. Paul, MN 55104 (612) 641-1955 (800) 926-4797 FAX (612) 641-1952 NIH/National Institute of Child Health and Human Development (NICHD) 9000 Rockville Pike Bethesda, MD 20892 (301) 496-5133 Association for Retarded Citizens of the United States P.O. Box 6109 Arlington, TX 76005 (817) 640-0204 (800) 433-0525 For information on genetics and genetic counseling referrals, please contact: March of Dimes Birth Defects Foundation 1275 Mamaroneck Ave. White Plains, NY 10603 (914) 428-7100 Alliance of Genetic Support Groups 35 Wisconsin Circle, Suite 440 Chevy Chase, MD 20815 (800) 336-GENE (301) 652-5553 References SMITH'S RECOGNIZABLE PATTERNS OF HUMAN MALFORMATION, 4th ed., Kenneth L. Jones, M.D., W.B. Saunders, Co. 1988. Pp. 170-3. MENDELIAN INHERITANCE IN MAN, 10th Ed.: Victor A. McKusick, Editor: Johns Hopkins University Press, 1992. Pp. 912-916. CECIL TEXTBOOK OF MEDICINE, 19th Ed.: James B. Wyngaarden, and Lloyd H. Smith, Jr., Editors; W.B. Saunders Co., 1990. Pp. 1146. BIRTH DEFECTS ENCYCLOPEDIA, Mary Louise Buyse, M.D., Editor-In-Chief; Blackwell Scientific Publications, 1990. Pp. 1408-1411. LOCALIZATION OF THE GENE ENCODING THE GABAA RECEPTOR BETA 3 SUBUNIT TO THE ANGELMAN/PRADER-WILLI REGION OF HUMAN CHROMOSOME 15, J. Wagstaff et al.; Am J Hum Gen (Aug 1991; 49(2)): Pp. 330-337. PRADER-WILLI SYNDROME: CURRENT UNDERSTANDING OF CAUSE AND DIAGNOSIS, M.G. Butler; Am J Med Genet (Mar 1990; 35(3)). Pp. 319-332.