Muscular Dystrophy, Becker

Muscular Dystrophy, Becker

National Organization for Rare Disorders, Inc.

Important

It is possible that the main title of the report Muscular Dystrophy, Becker is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.

Synonyms

  • Benign Juvenile Muscular Dystrophy
  • BMD
  • Progressive Tardive Muscular Dystrophy

Disorder Subdivisions

  • None

General Discussion

Becker muscular dystrophy is in the category of inherited muscle wasting diseases caused by a gene abnormality (mutation) that results in deficient or abnormal production of the dystrophin protein (dystrophinopathies). The abnormal gene is called DMD and is located on the X chromosome. Becker muscular dystrophy follows x-linked recessive inheritance so it mostly affects males, but some females are affected. Becker muscular dystrophy usually begins in the teens or early twenties and symptoms vary greatly between affected individuals. Muscle deterioration progresses slowly but usually results in the need for a wheel chair. Muscles of the heart deteriorate (cardiomyopathy) in some affected individuals, and this process can become life-threatening. Learning disabilities involving visual abilities may be present.

Symptoms

Symptoms of Becker muscular dystrophy usually begin in the teens or late twenties. Initial symptoms may include cramping during exercise and reduced stamina during exercise. Muscle gradually deteriorates in the hips, pelvis, thighs and shoulders that can lead to walking on toes with the stomach forward. Shortening of muscle fibers can result in the inability to move certain muscles (contractures). The progression of BMD is slower and more variable than Duchenne muscular dystrophy but usually results in the need for a wheel chair. The heart muscle is also affected and can result in feeling breathless, fluid accumulation in the lungs and swelling in the feet and lower legs. Dilated cardiomyopathy is the most common cause of death in individuals with BMD, and most affected individuals die in their mid 40's.



Approximately 5-10% of female DMD gene carriers have some symptoms of muscle weakness that progress slowly or not at all. Muscle weakness is frequently more severe on one side of the body (asymmetric).

Causes

Becker muscular dystrophy is caused by abnormalities (mutations) in the DMD gene that is responsible for the production of the dystrophin protein. Dystrophin is necessary for the stability and protection of muscle. The gene mutation causes the dystrophin protein to be shorter than normal and not function normally.



The DMD gene is located on the X chromosome and Becker muscular dystrophy follows x-linked recessive inheritance. Females have two X chromosomes but one of the X chromosomes is "turned off" and all of the genes on that chromosome are inactivated. Females who have a disease gene present on one of their X chromosomes are carriers for that disorder. Carrier females usually do not display symptoms of the disorder because it is usually the X chromosome with the abnormal gene that is "turned off". A male has one X chromosome and if he inherits an X chromosome that contains a disease gene, he will develop the disease. Males with X-linked disorders pass the disease gene to all of their daughters, who will be carriers. A male cannot pass an X-linked gene to his sons because males always pass their Y chromosome instead of their X chromosome to male offspring. Female carriers of an X-linked disorder have a 25% chance with each pregnancy to have a carrier daughter like themselves, a 25% chance to have a non-carrier daughter, a 25% chance to have a son affected with the disease, and a 25% chance to have an unaffected son.

Affected Populations

Becker muscular dystrophy occurs in approximately 1 in 30,000 male births.

Standard Therapies

Diagnosis

The diagnosis of Becker muscular dystrophy is based on physical symptoms, family history, an elevated concentration of creatine kinase (CK) in the blood indicating destruction of muscle, and molecular genetic testing. DMD is the only gene that has been associated with Becker muscular dystrophy and many different types of DMD gene mutations have been identified in individuals with this condition. Identification of a DMD gene mutation from molecular genetic testing confirms the diagnosis. If molecular genetic testing is performed and a DMD gene mutation is not found, a skeletal muscle biopsy is recommended to examine the appearance of the dystrophin protein.



Treatment

No specific treatment is available for Becker muscular dystrophy but quality of life and lifespan can be improved with appropriate care. Physical and occupational therapy can reduce or delay joint contractures. Surgery is sometimes recommended to treat contractures or scoliosis. Weight control can help to reduce stress on the heart and muscles. Corticosteroids are often prescribed to help slow down the loss of muscle function. Routine monitoring by a cardiologist is recommended.

Investigational Therapies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.



For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:



Tollfree: (800) 411-1222

TTY: (866) 411-1010

Email: prpl@cc.nih.gov



For information about clinical trials sponsored by private sources, contact:

www.centerwatch.com



In April of 2008, PTC Therapeutics, Inc. (PTC), announced the initiation of an international pivotal trial of PTC124 in patients with Duchenne/Becker muscular dystrophy (DMD/BMD) due to a nonsense mutation. The primary objective of this registration-directed Phase 2b trial is to demonstrate the efficacy of PTC124 as measured by improvements in the walking ability of patients with this progressive genetic disease.



PTC124 is a novel, orally delivered drug in development for the treatment of patients with genetic disorders due to a nonsense mutation, a type of mutation found in approximately 13% of patients with DMD. In this double-blind study, patients will be randomized to receive placebo, or one of two dose levels of PTC124, three times per day. Eligible patients will be boys with nonsense-mutation-mediated DMD/BMD who are at least 5 years of age and are able to walk at least 75 meters or approximately 80 yards in six minutes. PTC expects to enroll a total of 165 patients at approximately 35 investigational sites; all study subjects will undergo 48 weeks of blinded treatment. Thereafter, all participants, including those who have been receiving placebo, will be eligible to enroll in an open-label PTC124 extension study.



For more information please contact:

or more information:



Jane Baj

PTC Therapeutics, Inc.

(908) 912-9167

jbaj@ptcbio.com



OR



Sheryl Seapy

Pure Communications

(949) 608-0841

sheryl@purecommunicationsinc.com

References

TEXTBOOKS

Ascadi G. Becker Muscular Dystrophy. In: The NORD Guide to Rare Disorders, Philadelphia: Lippincott, Williams and Wilkins, 2003:622.



JOURNAL ARTICLES

Bushby KM and Gardner-Medwin D. The clinical, gentic and dystrophin characteristics of Becker muscular dystophy. I. Natural history [published erratum appears in J Neurol 1993 Jul;240 (7):453]j Neurol 240:98-104.



Hoffman EP, Fischbeck KH, Brown, et al. Characterization of dystrophin in muscle-biopsy specimens from patients with Duchenne's or Becker's muscle dystrophy. N Engl J Med 1998;318:1363-8.



Nolan MA Jones OD, Pederson RL, et al. Cardiac assessment in childhood carriers of Duchenne and Becker muscle dystrophies. Neuromuscul Disord 2003;13:129-32.



Palmucci L, Mongini T, Chido-Piat L, et al. Dystrophinopathy expressing as either cardiomyopathy or Becker dystrophy in the same family. Neurology 2000; 54:529-30.



Quinlivan R, Ball J, Dunckley M, et al. Becker muscle dystrophy presenting with complete heart block in the sixth decade. Neurology 1995;242:398-400.



FROM THE INTERNET

Kork BR, Darras BT, and Urion DK (Updated 10/4/04) Dystrophinopathies In: GeneReviews at GeneTests: Medical Genetics Information Resource (database online). Copyright, University of Washington, Seattle. 1997-2005. Available at http://genetests.org. Accessed 6/05.



McKusick VA ed. Online Inheritance in Man (OMIM). Baltimore, MD: The Johns Hopkins University: Entry No. 300376, Last Update: 4/2/02.

Resources

Parent Project Muscular Dystrophy

401 Hackensack Avenue, 9th Floor

Hackensack, NJ 07601

USA

Tel: (201)944-9985

Fax: (201)944-9987

Tel: (800)714-5437

Email: info@parentprojectmd.org

Internet: http://www.parentprojectmd.org



Muscular Dystrophy Association

3300 East Sunrise Drive

Tucson, AZ 85718-3208

USA

Tel: (520)529-2000

Fax: (520)529-5300

Tel: (800)572-1717

Email: mda@mdausa.org

Internet: http://www.mda.org/



Muscular Dystrophy Campaign

61 Southwark Street

London, SE1 0HL

United Kingdom

Tel: 02078034800

Email: info@muscular-dystrophy.org

Internet: http://www.muscular-dystrophy.org



NIH/National Institute of Neurological Disorders and Stroke

P.O. Box 5801

Bethesda, MD 20824

Tel: (301)496-5751

Fax: (301)402-2186

Tel: (800)352-9424

TDD: (301)468-5981

Internet: http://www.ninds.nih.gov/



Society for Muscular Dystrophy Information International

P.O. Box 7490

Bridgewater

Nova Scotia, B4V 2X6

Canada

Tel: 9026853961

Fax: 9026853962

Email: smdi@auracom.com

Internet: http://www.nsnet.org/smdi/



New Horizons Un-Limited, Inc.

811 East Wisconsin Ave

P.O. Box 510034

Milwaukee, WI 53203

USA

Tel: (414)299-0124

Fax: (414)347-1977

Email: horizons@new-horizons.org

Internet: http://www.new-horizons.org



Genetic and Rare Diseases (GARD) Information Center

PO Box 8126

Gaithersburg, MD 20898-8126

Tel: (301)251-4925

Fax: (301)251-4911

Tel: (888)205-2311

TDD: (888)205-3223

Internet: http://rarediseases.info.nih.gov/GARD/



Madisons Foundation

PO Box 241956

Los Angeles, CA 90024

Tel: (310)264-0826

Fax: (310)264-4766

Email: getinfo@madisonsfoundation.org

Internet: http://www.madisonsfoundation.org



Let Them Hear Foundation

1900 University Avenue, Suite 101

East Palo Alto, CA 94303

Tel: (650)462-3174

Fax: (650)462-3144

Email: info@letthemhear.org

Internet: http://www.letthemhear.org



DuchenneConnect

Emory University, Department of Human Genetics

2165 N. Decatur Road

Atlanta, GA 30033

Tel: (404)778-0553

Fax: (404)935-0636

Email: coordinator@duchenneconnect.org

Internet: http://www.duchenneconnect.org



Child Neurology Foundation

2000 West 98th Street

Bloomington, MN 55431

USA

Tel: (952)641-6100

Fax: (952)881-6276

Tel: (877)263-5430

Email: jstone@childneurologyfoundation.org

Internet: http://www.childneurologyfoundation.org



Medical Home Portal

Dept. of Pediatrics

University of Utah

P.O. Box 581289

Salt Lake City, UT 84158

Tel: (801)587-9978

Fax: (801)581-3899

Email: mindy.tueller@utah.edu

Internet: http://www.medicalhomeportal.org



For a Complete Report

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