$Unique_ID{BRK04220} $Pretitle{} $Title{Sialidosis} $Subject{Sialidosis Cherry Red Spot Myoclonus syndrome Mucolipidosis I ML I Lipomucopolysaccharidosis Type I Sialidosis Type I Sialidosis Type II} $Volume{} $Log{} Copyright (C) 1986, 1990 National Organization for Rare Disorders, Inc. 302: Sialidosis ** IMPORTANT ** It is possible the main title of the article (Sialidosis) is not the name you expected. Please check the SYNONYMS listing to find the alternate names and disorder subdivisions covered by this article. Synonyms Cherry Red Spot - Myoclonus syndrome Mucolipidosis I ML I Lipomucopolysaccharidosis Type I DISORDER SUBDIVISIONS Sialidosis Type I Sialidosis Type II 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. The Mucolipidoses (ML II & ML III) are a family of hereditary disorders in which enzyme deficiencies cause both complex carbohydrates (mucopolysaccharides) and certain fatty substances (mucolipids) to accumulate in body tissues without excess mucopolysaccharides in the urine. (For more information on the mucolipidoses, choose "ML Disorder" as your search term in the Rare Disease Database.) Sialidosis (previously called Mucolipidosis I) is a very rare recessive hereditary disorder caused by decreased activity of the enzyme gamma- neuraminidase. Patients have normal urinary mucopolysaccharides, elevated urinary oligosaccharides containing salic acid, mild mental retardation, cherry-red spots on the retina (interior back portion of the eyeball), and signs of neurological involvement in older children. Two forms of Sialidosis are known. Sialidosis Type I has primary eye and muscle involvement (myoclonus). Sialidosis Type II has eye and muscle involvement plus mild coarsening of the face, skeletal changes and mild mental retardation. Symptoms Sialidosis (Lipomucopolysaccharidosis Type I) is characterized by moderate developmental retardation which usually occurs during late infancy. As the disease progresses, the children manifest short stature with a disproportionately short trunk, an enlarged liver and spleen (hepatosplenomegaly), hernias, moderate to severe mental retardation, impaired hearing and cherry-red macular spots on the retina of the eye. Progressive loss of vision, often severe, may be associated with impaired color vision or night blindness. After about 5 years, there are progressive signs of a dysfunction of the white matter of the nervous system such as seizures with shocklike muscular contractions (myoclonus); decreased muscle strength; diminished tonus of the muscles (hypotonia); uncoordinated movements (ataxia); tremor; rapid movements of the eyeballs (nystagmus); irregular reflexes; and reduced nerve conduction velocity. In older patients, the electro-encephalogram (EEG) shows peculiar complexes of high-frequency polyspikes and sharp waves. Generalized abnormal bone development occurs. Opacities of the cornea of the eye may sometimes develop. Causes Sialidosis is an autosomal recessive inherited disorder in which the activity of the enzyme gamma-neuraminidase is deficient. (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 recessive disorders, the condition does not appear unless a person inherits the same defective gene from each parent. If one receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will show no symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is twenty-five percent. Fifty percent of their children will be carriers, but healthy as described above. Twenty-five percent of their children will receive both normal genes, one from each parent and will be genetically normal.) Affected Population Sialidosis affects males as often as females. Siblings of patients have a 1 in 4 chance to be affected. Therapies: Standard Carriers of Sialidosis can be detected by an enzyme assay in cultured fibroblasts, making prenatal diagnosis possible. Genetic counseling is advised for families affected by this disorder. Treatment of Sialidosis is symptomatic and supportive. Seizures may be controlled by a variety of anticonvulsant medications. 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 Sialidosis are now under investigation. 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 therapy may someday be made available to people with genetic disorders such as Sialidosis. This disease entry is based upon medical information available through February 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 Sialidosis, please contact: National Organization for Rare Disorders (NORD) P.O. Box 8923 New Fairfield, CT 06812-1783 (203) 746-6518 MPS (Mucopolysaccharidoses) Research Funding Center, Inc. 1215 Maxfield Road Hartland, MI 48029 (313) 363-4412 The MPS Society, Inc. 17 Kramer Street Hicksville, NY 11801 (516) 931-6338 Society of Mucopolysaccharide Diseases, Inc. 382 Parkway Blvd. Flin Flon, Manitoba, Canada R8A 0K4 Society of MPS Diseases 30 Westwood Drive Little Chalfont, Bucks, England National Digestive Diseases Information Clearinghouse Box NDDIC Bethesda, MD 20892 (301) 468-6344 International Tremor Foundation 360 W. Superior St. Chicago, IL 60610 (312) 664-2344 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 BIRTH DEFECTS COMPENDIUM, 2d ed.: Daniel Bergsma, ed.; March of Dimes, 1979. P. 724. MENDELIAN INHERITANCE IN MAN, 6th ed.: Victor A. McKusick; Johns Hopkins University Press, 1983. Pp. 832-833.