$Unique_ID{BRK03831} $Pretitle{} $Title{Hunter Syndrome} $Subject{Hunter Syndrome Mucopolysaccharidosis Type II MPS II MPS Disorder MPS IIA MPS IIB} $Volume{} $Log{} Copyright (C) 1986, 1987, 1988, 1990 National Organization for Rare Disorders, Inc. 282: Hunter Syndrome ** IMPORTANT ** It is possible the main title of the article (Hunter Syndrome) is not the name you expected. Please check the SYNONYMS listing to find the alternate names and disorder subdivisions covered by this article. Synonyms Mucopolysaccharidosis Type II MPS II MPS Disorder DISORDER SUBDIVISIONS MPS IIA MPS IIB 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. Mucopolysaccharidoses (MPS Disorders) are a group of rare genetic disorders caused by the deficiency of one of ten specific lysosomal enzymes resulting in an inability to metabolize complex carbohydrates (mucopolysaccharides) into simpler molecules. The accumulation of these large, undegraded mucopolysaccharides in the cells of the body causes a number of physical symptoms and abnormalities. The most prevalent form of MPS Type II is called Hunter Syndrome. The disorder can be manifested in a mild or a severe form. Symptoms Two types of Hunter syndrome (MPS II) have been recognized, mild and severe, both with the same enzymatic deficiency, iduronate sulfatase. The severe form of Hunter syndrome has features similar to Hurler syndrome except for the lack of corneal clouding and slower progression of physical involvement and mental retardation. In the severe form of this disorder, physical and mental development reach a peak at 2-4 years of age with subsequent deterioration. Recurrent urinary and upper respiratory infections, a chronic runny nose, liver enlargement, joint stiffness and growth failure commonly occur with the severe from of Hunter syndrome. Coarsening of the facial features with thickening of the nostrils, lips and tongue usually occur between 2 and 4 years of age. Hydrocephalus is commonly found in this form of Hunter syndrome after 4 years of age. (For more information, choose "hydrocephalus" as your search term in the Rare Disease Database.) Thick skin, short neck, widely spaced teeth, and hearing loss of varying degree are also commonly present. Nodular skin lesions on the arm or the posterior chest wall, extra-high arched feet (pes cavus) and diarrhea also may occur. In the mild form of Hunter syndrome, mental function is usually normal and physical deterioration is greatly reduced compared to the severe form. Complications of the mild form of the disorder may include heart, coronary and valvular disease, hearing impairment, reduced circulation in the hands due to compression of veins in the wrist (carpal tunnel syndrome), and joint stiffness which can result in loss of hand function. Causes Hunter Syndrome is an x-linked recessive hereditary disorder, in which a deficiency in the enzyme odirpmate sulfatase causes the physical and mental deterioration. (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. X-linked recessive disorders are conditions which are coded on the X chromosome. Females have two X chromosomes, but males have one X chromosome and one Y chromosome. Therefore in females, disease traits on the X chromosome can be masked by the normal gene on the other X chromosome. Since males have only one X chromosome, if they inherit a gene for a disease present on the X, it will be expressed. Men with X-linked disorders transmit the gene to all their daughters, who are carriers, but never to their sons. Women who are carriers of an X-linked disorder have a fifty percent risk of transmitting the carrier condition to their daughters, and a fifty percent risk of transmitting the disease to their sons.) Affected Population Hunter Syndrome affects only males, with symptoms becoming apparent at approximately 2-4 years of age. The disorder occurs in 1 out of 100,000 live births. Related Disorders There are many types of Mucopolysaccharidoses. (For more information, choose "MPS Disorder" as your search term in the Rare Disease Database.) DiFerrante syndrome (Mucopolysaccharidosis VIII) is a disorder described in a single patient with clinical and biochemical features of Morquio and Sanfilippo syndromes. The disorder had been reported to be due to a deficiency of glucosamine-6-sulfate sulfatase. Subsequently, this disorder was called MPS VIII (DiFerrante syndrome). Dr. DiFerrante later found that the enzyme was normal in his patient, and the disorder had been misdiagnosed. Therefore, DiFerrante syndrome is not a valid medical disorder. The Mucolipidoses are a family of similar disorders, producing symptoms very much like those of the Mucopolysaccharidoses. I-cell disease, or Mucolipidosis Type II, resembles Hurler syndrome and the two disorders are very difficult to distinguish. I-cell disease has similar physical and mental deterioration as MPS I, but usually occurs earlier and is more severe. I-cell disease is characterized by diffused deficiency of lysosomal enzymes within the cell and is not associated with excretion of mucopolysaccharides in the urine. (For more information, choose "I-Cell Disease" as your search term in the Rare Disease Database.) Pseudo-Hurler Polydystrophy (Mucolipidosis III) is also transmitted by autosomal inheritance, but it is characterized by a deficiency of multiple lysosomal enzymes needed to break down mucopolysaccharides. ML III affects males more often than females, and can be identified by such symptoms as claw-like hands, somewhat coarse facial features, dwarfism and pain in the hands. Intelligence tends to be normal in most patients, but mild mental retardation is possible. Ganglioside Sialidase Deficiency (Mucolipidosis IV) is a disorder of unknown cause characterized by early clouding of the cornea, mild to moderate mental retardation and enlargement of spleen and liver. (For more information on the Mucolipidoses, choose "ML Disorder" as your search term in the Rare Disease Database.) Therapies: Standard Treatment of Hunter Syndrome is symptomatic and supportive. Hernias and joint contractures may be corrected by surgery. Surgical implantation of a ventricular shunt may be used to treat possible hydrocephalus. Hearing devices may be prescribed to treat hearing loss. Physical therapy, medical and genetic counseling services may be helpful to patients and families. Prenatal diagnosis is now possible for this disorder. Therapies: Investigational Since prenatal diagnosis is now possible through amniocentesis and sampling of a tissue layer in the embryo (chorionic villus sampling), new treatments aimed at checking early development of Hunter Syndrome are now under study. One method involves replacing defective enzymes via enzyme replacement therapy and/or bone marrow transplants. Scientific study of gene replacement in animal models raises the hope that gene replacement may someday be made available to people with genetic disorders such as Hunter Syndrome. The Mayo Clinic is investigating the use of Alpha Interferon as a treatment for Hunter Syndrome. For more information, physicians can contact: Morie A. Gertz, M.D. Dept. of Hematology & Internal Medicine Mayo Clinic Rochester, MN 55905 (507) 284-2511 This disease entry is based upon medical information available through January 1990. 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 Hunter Syndrome, please contact: National Organization for Rare Disorders (NORD) P.O. Box 8923 New Fairfield, CT 06812-1783 (203) 746-6518 National MPS Society 17 Kramer Street Hicksville, NY 11801 (516) 931-6338 MPS (Mucopolysaccharidoses) Research Funding Center, Inc. 1215 Maxfield Road Hartland, MI 48029 (313) 363-4412 Society of Mucopolysaccharide Diseases, Inc. 382 Parkway Blvd. Flin Flon, Manitoba, Canada R8A OK4 Society of MPS Diseases 30 Westwood Drive Little Chalfont, Bucks, England National Digestive Diseases Information Clearinghouse Box NDDIC Bethesda, MD 20892 (301) 468-6344 For information on genetics and genetic counseling referrals, please contact: March of Dimes Birth Defects Foundation 1275 Mamaroneck Avenue 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 MPS Society Brochure MPS Research Funding Center Bulletin BIRTH DEFECTS COMPENDIUM, 2nd ed.: Daniel Bergsma, ed; March of Dimes, 1979. Pp. 730. MENDELIAN INHERITANCE IN MAN, 6th ed.: Victor A. McKusick; Johns Hopkins University Press. 1983. Pp. 836.