The frequency with which such genetic mutations trigger the clinical onset of disease is known as penetrance. Machado-Joseph disease presents a 94.5% penetrance, which means that 94.5% of the mutation carriers will develop the symptoms during their lives, and less than 5% will remain free of symptoms. Because the intensity and range of symptoms are highly variable among the affected individuals, it is difficult to determine the prognosis for a given individual. As MJD progresses slowly, most patients survive until middle age or older.
Fenichel, Gerald M. Clinical Pediatric Neurology: A Signs and Symptoms Approach, 4th ed. Philadelphia: W. B. Saunders Company, 2001.
Dystonia Medical Research Foundation. 1 East Wacker Drive, Suite 2430, Chicago, IL 60601-1905. (312) 755-0198; Fax: (312) 803-0138. firstname.lastname@example.org. <http://www.dystonia-foundation.org>.
International Machado-Joseph Disease Foundation, Inc. P.O. Box 994268, Redding, CA 96099-4268. (530) 246-4722. MJD@ijdf.net. <http://www.ijdf.net>.
National Ataxia Foundation (NAF). 2600 Fernbrook Lane, Suite 119, Minneapolis, MN 55447-4752. (763) 553-0020; Fax: (763) 553-0167. email@example.com. <http://www.ataxia.org>.
National Organization for Rare Disorders (NORD). P.O. Box 1968 (55 Kenosia Avenue), Danbury, CT 06813-1968. (203) 744-0100 or (800) 999-NORD (6673); Fax: (203) 798-2291. firstname.lastname@example.org. <http://www.rarediseases.org>.
Worldwide Education & Awareness for Movement Disorders (WE MOVE). 204 West 84th Street, New York, NY 10024. (212) 875-8312 or (800) 437-MOV2 (6682); Fax: (212) 875-8389. email@example.com. <http://www.wemove.org>.
Sandra Galeotti, The Gale Group Inc., Gale, Detroit,