$Unique_ID{BRK03413} $Pretitle{} $Title{Achondroplasia} $Subject{Achondroplasia Chondrodystrophy Chondrohystrophia Chondrodystrophia Fetalis Hypoplastic Chondrodystrophy Parrot Syndrome Achondroplastic Dwarfism Dwarfism} $Volume{} $Log{} Copyright (C) 1986, 1990, 1992, 1993 National Organization for Rare Disorders, Inc. 80: Achondroplasia ** IMPORTANT ** It is possible that the main title of the article (Achondroplasia) is not the name you expected. Please check the SYNONYMS listing to find the alternate name and disorder subdivisions covered by this article. Synonyms Chondrodystrophy Chondrohystrophia Chondrodystrophia Fetalis Hypoplastic Chondrodystrophy Parrot Syndrome Achondroplastic Dwarfism Information on the following diseases can be found in the Related Disorders section of this report: Dwarfism 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. Achondroplasia is an inherited congenital disorder that results in very short stature (dwarfism) due to an impairment in the ability of cartilage to form bone (endochondral bone formation). Craniofacial abnormalities are also associated with Achondroplasia. Symptoms Infants born with Achondroplasia typically have an arched or "dome-like" (vaulted) skull to adapt to the abnormally enlarged brain (megalencephaly) that is characteristic in this syndrome. This results in a very broad forehead. Excessive accumulation of fluid around the brain (hydrocephalus) may also be present. Compression of the brain stem may occur in some children with Achondroplasia resulting in a life-threatening condition. (For more information on this disorder, choose "Hydrocephalus" as your search term in the Rare Disease Database.) Infants with Achondroplasia typically have a low nasal bridge. Arms and legs are usually very short and the trunk of the body appears long in comparison. The hands of children with this disorder are generally short and broad. The index and middle finger are typically close together as are the ring finger and the pinkie, giving the hand a three pronged (trident) appearance. An abnormal condition of the spine characterized by the outward (convex) curvature of the upper back (dorsal kyphosis) is usually present in children with this disorder and their legs may be bowed. Most adult males with Achondroplasia are under 4 feet 6 inches tall, while females are typically 3 inches shorter than males. Children with Achondroplasia may also have deformities of the rib cage including the excessive curvature or "cupping" of the ribs. Achondroplasia does not cause any impairment or deficiencies in mental abilities. The life expectancy of infants over the age of 12 months is normal. Causes Achondroplasia is inherited as an autosomal dominant genetic trait. Human traits, including the classic genetic diseases, are the product of the interaction of two genes, 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 other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is fifty percent for each pregnancy regardless of the sex of the resulting child. Children of fathers of advanced age are more likely to be born with a spontaneous case (de novo mutation) of Achondroplasia. In these cases the Achondroplasia is not inherited through autosomal dominant genes, and the exact cause is unknown. Affected Population Achondroplasia is a rare disorder that affects males and females in equal numbers. This disorder begins in the developing fetus (congenital) and is one of the most common forms of skeletal dysplasia that causes dwarfism. Approximately 5 to 15 newborns in 100,000 are affected by this disorder in the United States. Related Disorders Symptoms of the following disorders can be similar to those of Achondroplasia. Comparisons may be useful for a differential diagnosis: Dwarfism may be associated with many other disorders. Some of these include Diastrophic Dysplasia, Osteogenesis Imperfecta, Thanatophoric Dysplasia, Hypochondroplasia, Constitutional Growth Delay, Growth Hormone Delay, and Russell-Silver Syndrome. Achondroplasia may be distinguished from other forms of short-limbed stature through examination by a physician as well as x-rays studies and/or magnetic resonance imaging. Many forms of dwarfism are not associated with an abnormally enlarged head or other symptoms of Achondroplasia that are characteristic for the disorder. (For more information on these disorders, choose "Diastrophic Dysplasia," "Osteogenesis Imperfecta," "Thanatophoric Dysplasia," "Hypochondroplasia," "Constitutional Growth Delay," "Growth Hormone Delay," and "Russell-Silver" as your search terms in the Rare Disease Database.) Therapies: Standard Ultrasonography or magnetic resonance imaging (MRI) of the brain in infancy may be done to determine the presence of hydrocephalus which is sometimes associated with Achondroplasia. Orthopedic surgery and physical therapy may be beneficial in the management of this disorder. Genetic counseling may also be useful. Little People of America is an organization providing social services for persons with Achondroplasia. The organization also acts as an advocate on their behalf (see Resources Section of this report). Therapies: Investigational The Titanium Rib Project is underway to implant expandable ribs in children with disorders such as Achondroplasia and other disorders involving missing, underdeveloped, or otherwise malformed rib cages, and/or chest walls. Birth defects, fused ribs, or hypoplastic chests may be improved using the titanium ribs that can be expanded as the child grows. More research is needed to determine the long-term safety and effectiveness of these artificial ribs. People who are interested may have their physicians contact: Dr. Robert Campbell Santa Rosa Children's Hospital 519 W. Houston St. San Antonio, TX 78207-3198 (512) 567-5125 Research on genetic defects and their causes is ongoing. The National Institutes of Health (NIH) is sponsoring the Human Genome Project that is aimed at mapping every gene in the human body and learning why they sometimes malfunction. It is hoped that this new knowledge will lead to prevention and treatment of genetic disorders in the future. This disease entry is based upon medical information available through May 1993. 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 Achondroplasia, please contact: National Organization for Rare Disorders (NORD) P.O. Box 8923 New Fairfield, CT 06812 (203) 746-6518 The National Arthritis and Musculoskeletal and Skin Diseases (NIAMS) Information Clearinghouse Box AMS Bethesda, MD 20892 (301) 495-4484 Little People of America P.O. Box 633 San Bruno, CA 94066 (415) 589-0695 International Center for Skeletal Dysplasia St. Joseph Hospital 7620 York Rd. Towson, MD 21204 (301) 337-1250 Human Growth Foundation (HGF) 7777 Leesburg Pike P.O. Box 3090 Falls Church, VA 22043 (703) 883-1773 (800) 451-6434 The Magic Foundation 1327 N. Harlem Ave. Oak Park, IL 60302 (708) 383-0808 Short Stature Foundation 17200 Jamboree Rd., Suite J Irvine, CA 92714-5828 (714) 474-4554 (800) 24-DWARF Parents of Dwarfed Children 11524 Colt Terrace Silver Spring, MD 20902 Association for Research into Restricted Growth 2 Mount Court 81 Central Hill London SE 19 1 BS England 01-678-2984 For Genetic Information and Genetic Counseling Referrals: March of Dimes Birth Defects Foundation 1275 Mamaroneck Ave. White Plains, NY 10605 (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. 298-303. MENDELIAN INHERITANCE IN MAN, 10th Ed.: Victor A. McKusick, Editor: Johns Hopkins University Press, 1992. Pp. 10-11. CECIL TEXTBOOK OF MEDICINE, 19th Ed.: James B. Wyngaarden, and Lloyd H. Smith, Jr., Editors; W.B. Saunders Co., 1990. Pp. 1435-36. THE MERCK MANUAL, 16th Ed.: Robert Berkow Ed.; Merck Research Laboratories, 1992. Pp. 2255-2256. BIRTH DEFECTS ENCYCLOPEDIA, Mary Louise Buyse, M.D., Editor-In-Chief; Blackwell Scientific Publications, 1990. Pp. 11-12. NELSON TEXTBOOK OF PEDIATRICS, 14th Ed.; Richard E. Behrman et al; W.B. Saunders Co., 1992. Pp. 1733-34. MAGNETIC RESONANCE IMAGING IN THE ASSESSMENT OF MEDULLARY COMPRESSION IN ACHONDROPLASIA. I.T. Thomas; Am J Dis Child (Sep 1988; 142(9)). Pp. 989-992. GROWTH HORMONE THERAPY IN ACHONDROPLASIA. W.A. Horton; Am J Med Genet (Mar 1992; 42(5)). Pp. 667-70.